Assuming he is using a glow 2 cycle I would say the uniflow tank is the way to go. Is his intent to fly in competition? If yes would likely need 4oz (35 - 40 engine) 3oz might be ok if FP 25. If a 4 stroke then that tank should work, they like standard venting.

Best,    DennisT

That tank will work fine on a profile. For doing some mild flying it is a good choice, but you do have other good options, too. A few comments:

(Forgive me if you already have considered all of these....)

--Compare the position of the middle of the tank volume to the jet hole in the spraybar. The better these match up laterally, the easier it will be to get a steady engine run. With a profile plane, the engine is (almost always) side-mounted, so the tank position is not as bad as you might assume when comparing it to an upright engine in a full fuselage model. Most spraybars are 1/2" from the bottom of the engine mounting lugs.

--The tank you show is the "medium wedge" meaning it is only 1-3/4" wide, not the full 2".  This helps a lot to even out the run of the engine from the beginning of the tank to the end of the tank. The geometry (hydraulics) say that there is too much pressure head when the tank is full, and too little at the end. So the engine will continue to speed up as the amount of fuel in the tank is reduced. A wide tank makes this problem worse.

--The speedup can be mitigated to a certain extent by running pressure from the muffler (if installed) to one of the tank vents--yes, even on a standard vent tank like the one you show. But you must cap off the other vent.

--You can also mitigate using a tank plumbed for uniflow. In many (not all) applications this helps. And, you can combine muffler pressure with a uniflow setup. An awful lot of sport flyers consider this configuration first and never look back.

--You can fit a longer tank on the Twister--there's a lot of room up front unless the nose will be built non-standard. I would try for 4 or 4-1/2 oz capacity leaving you more options on tuning, fuel mixes, and engine changes. You don't have to fill the tank full but be sure it is somewhere over half full or you'll never get it started....

--I am currently using a Brodak "oval" tank with an OS .46LA on a Twister. I replumbed it for uniflow so that it is now very similar to their BH-594 5 oz tank. It works very well in this combination. That might not always be true for other combinations. The oval tanks have a larger height dimension, and this can make some engines run less steady.

--Different engines have different fuel draw capabilities. Some are known to be weaker. A larger venturi in a given engine will have less draw.

--The Fox .35 has pretty good draw, but you really help yourself out with the medium wedge geometry. The OS .40 should behave pretty much the same as the .46.

--With the Fox, I like to run a lot of castor lubricant. Real long tanks have long internal tubing that cause more resistance to flow. This only seems to be a problem when it gets real cold out. Keeping your fuel warm in the winter helps. Taking off the fuel filter between the tank and engine helps too. I haven't had any real issues at 50F using 29% castor with the Fox.

--As another reference, I have a profile plane with a McCoy .19 and a medium wedge standard vent tank. It has a very nice engine run. But the nose was too short (Jr. Flite Streak) to fit a long enough tank to make for satisfying flights. An oval tank would fit more fuel into the given length, but the engine did not like the deeper and wider tank. So I got a longer but annoying engine run....

There are a number of choices that are going to work. Good luck!

Dave