A starting point is the Feb 2026 article by Fred Cronenwett in Model Aviation "A Brief History of CL Throttle Control"  https://www.modelaviationdigital.com/modelaviation/library/item/february_2026/4316308/

There is no right or wrong answer.  As Fred described, there are many different ways to accomplish what you are asking about.  When you read the article...
1) You see a photo of Fred with a "airplane" transmitter hanging off his belt.  Many pilots use this method - standard throttle control on the left joystick with retracts and flaps tied to toggle switches on the top of the transmitter.
2) You see a photo of Mike McHenry simply holding a "car" transmitter in his left hand with the model handle in the right hand.  He uses the standard transmitter trigger for the throttle.  Note that this only works if your model is throttle only without retracts / flaps.
3) You see a photo of me flying with the Spektrum DX5 transmitter integrated with my handle.  Since I do not like to fly throttle on a trigger (just my preference), I use the steering wheel for throttle control (after removing the centering spring).  The transmitted has multiple toggle buttons on the stem - one is linked to my flaps.  I plug the throttle into the receiver "steering" channel and the flaps into the receiver "aux" channel.  The setup took a little transmitter programming (trial and error) to get the endpoints correct, but now I fly all my planes off the same DX5 transmitter.
4) Not shown, but YES, you can completely dismantle the transmitter and repackage all the components in a box that hangs off you handle.  Need to be careful doing this so that you do not ruin the transmitter.

One issue caught me offguard.  For Spektrum radios, "ground" receivers (cars) only bind with "ground" transmitters, while "air" receivers (planes) only bind with "air" transmitters.  You cannot mix and match.

Before you decide, think about how you like to fly - one hand or two?  Are you OK with a throttle trigger?  I like everything at my fingertips so that I do not have to take my eyes off the plane when searching for that toggle switch.

PM me if you want to talk - this might be more of a conversation instead of a post.

thank you for the info. I am not going to do this as I have an airplane radio with lots of receivers that I use already with no mods needed. I am used to flying with it with the belt clip. the recievers for the airplane radio are way cheaper than the car receivers. Having to mod the car radio is more work than using the airplane radio . The only reason I might do this is if I can't sell the r/c vehicle that uses this radio?

thank you for the info. I am not going to do this as I have an airplane radio with lots of receivers that I use already with no mods needed. I am used to flying with it with the belt clip. the recievers for the airplane radio are way cheaper than the car receivers. Having to mod the car radio is more work than using the airplane radio . The only reason I might do this is if I can't sell the r/c vehicle that uses this radio?

If there is nothing forcing you to change setup (ie, old transmitter died), and you are comfortable with the belt clip, then I would say do not change. 
When I switched from transmitter in a tray (I fly RC that way) to the car radio on the handle, it took some time to get used to the difference.  I was forced to change because I was flying on an older Airtronics radio that I was concerned about.  Many practice flights to make the transition.

I am working on this right now. Go to Amazon and search "Hot RC". They have a four channel pistol grip Tx with 2 Rx's for $36.00, The handle is hollow to hold the battery pack. I moved the battery to the outside, and fitted an aluminum handle frame inside the plastic shells, For extra strength I potted in with epoxy and microballoons so the handle is more solid to hold the pull test.

Throttle and the steering joystick are the two proportional channels, and there are also 2 push button non proportional channels. For $36 with 2 receivers, how can you go wrong? I am going to use mine for carrier. besides the throttle, I will use full left steering to release the line slider, and full right steering to drop the hook. This way I can get both functions with a single servo and single channel. Ultimately, I will write a full article on this. If I can't get AMA to print it, I will submit it to the Carrier Society Newsletter and send it to Pete Bauer as well.

Pete, in carrier we are constantly moving the throttle, so the trigger is appropriate. In scale, you don't constantly jockey the throttle, you typically set an RPM for a given task (except landing, of course). Did you reach that conclusion consciously, or did it just work out better for you?

Matt

The big question you need to decide is how many channels you need and then, are a traditional stick, toggle or a dial. And what they are going to operate.

I like to use a 3 position toggle for flaps
2 position for retracts, but a 3 position will also work for retracts, it just won't do anything at the middle position

You will find that you are always making slight adjustments with the throttle especially during landing and takeoff. The traditional transmitter will stay the position you leave it if you take your finger off the throttle stick. If it's windy and you need to add more power you can quickly change the throttle setting.

The Hot RC item has Merit like Bill showed with his modifications.

However I really do like these features that come with a modern 2.4 Ghz transmitter
1. Model memory
2. End point adjustment
3. Servo reversing
4. Servo speed adjustment (allows flaps to lower slowly instead of moving quickly to the down or up position)
5. Ability to select the toggle switch for a specific channel. Example for channel 5 I select select a specific toggle switch for flaps and another for retracts on channel 6

When I fly my SBD Dauntless with throttle, flaps and retracts you have to look closely to see how I control the throttle, raise or lower the flaps, then the retracts with small movements of my fingers

Fred

I am building another transmitter handle with the Hot RC transmitter, and taking pictures as I go to supplement a how-to article. Possibly of interest, this one has a 4x1100 mAh Ni-MH battery inside the hand grip.

The aluminum is 1/8" x 3/4", out of the rack at the home improvement store. I built a bender that is very similar in design to the K&S wire bender. There are lots of places that I can fudge the bends a little bit if it all doesn't line up perfectly. I also have a Harbor Freight bending brake that I use sometimes for simpler handle shapes.