The tie-wraps you are probably going to use do not need to be very wide.  Why cut slots when a simple drilled hole will do?  I suppose if you are dead set on slots, then a Dremel tool with a small router bit could be used.  It would no doubt be a freehand operation as successful as your steady hand.

I use the tie wrap method and simply drill holes for the wrap to go thru.

Drill 2 small holes (1/16" bit) about 3/8" apart,  cut out material between holes with hobby knife.

Been mounting my tanks this way for quite some time. I cheat and use my mill before I install the wing. Found and ordered a couple extra long small end mills off the net. They are long enough to go all the way through both doublers and 1/2 inch balsa. Have to use a low feed speed but they turn out looking, well like they were machined.

Before I bought the end mils I just drilled two small holes next to each other and used jewlers files to clean out the material between the holes.

See Howard, now that's just mean. Does that mean that using a post cure oven is a violation?

How about this?  http://durafix.com/blades/copingsaw/

Howard have you used a saw like this?  I have seen them but don't know how much practice I would need before I tried it on a plane.  I am leaning toward smaller wraps through drilled holes.
Steve

Howard have you used a saw like this? 

No.  I saw the question, admired your wanting the slots to be just right, figured that something like this saw ought to exist, then found it with Google. 

Where do we get the stuff? (clips, etc)  Ed

Bob that's exactly the solution I've been looking for! Very tidy and functional.  HD and Lowe's have the cable keepers in a couple of different colors; black, brown, and white.

On seeing this, I was reminded of a completely different cable tie mount that I have seen in the Oz equivalent to Radio Shack.



Aircraft Spruce sells them in large quantities http://www.aircraftspruce.com/catalog/elpages/cabletiemounts.php

This a top down view and I build them like this because it maintains a wet uniflow vent wet better than any other design I'm aware of. This is important because it keeps the engine from going rich at the wrong time per slosh slosh and the uniflow becomes unsubmerged. When the uniflow (naked silicone tube next to sintered bronze DurBo filter) finds itself in air and not fluid, the engine doesn't have to suck as hard as it did when the tank was full so it goes rich at just the wrong time....badness.
You must use a sintered bronze filter for this setup to work because the surface tension of the fuel won't allow any air to be sucked through the pickup which is the bronze thingy.
A 5/32 extender is soldered to the bronze filter to provide room to solder the 1/32 music wire loop which traps the naked silicone uniflow tube.
Looking straight at the cap which houses all the tubes finds the uniflow vent @ 9, the overflow @ 2 and the engine feed line @ 5.
Got to tweak the dickens out of the copper tubes that transition through the cap to make sure the clunk falls dead center when held vertical and that there are no binds in clunk action.....professional real estate management. The clunk must also be symmetrically located when the plane is held either upright or inverted.
The overflow is cut real short and a silicone extender is added because you can't get the thing together if you don't. Also helps to rotate the overflow @ 90° outboard when installing cap, then rotating back vertical once all together.

The big issue with this setup is you have to move the whole tank up or down to adjust for even speeds inside and out. No problem on a profile and mount @ 3/16 above engine centerline. Also, on a profile, don't build an adjustable tank saddle. Just use some Home Depot eyelets that you will have to cut open with a Dremel. Sanitary and slick with minimal additional outboard location....the main enemy of all profile set-ups. Sorry if it's not right out of the gate. Plug and redrill when you get home to achieve correct height. Additionally, it is wise to build an angled silicone foot for the tank to seat on with a slight outboard bias. Make sure the tank sits widest part is against the fuse to mitigate excessive centrifugal loading per engine thinks liquid going too far uphill once tank half empty and too lean run-away is the standard result. Use the blue and white tube of GE silicone (again available @ HD) and some wax paper. Rough up fuse side tank base, blob silicone and let rest a day or two on flat surface before separating from wax paper.

If you've got the room, this dude is a solid performer and make sure to pressure test capped off with syringe and coffee can full of water prior to installation.

If center clamp screw leaks, some professional grade black silicone seal will remedy and I like to use a washer under the screw as well.

Best,
Grady

I think slots look much better than clips, hooks or any added hardware that isn't really needed. This is my OTS Ringmaster and one I did before I started doing them on my mill.

How does inboard work with a big fat 1/4 - 1/2 vibration dampening inboard balsa trippler or cheek that's always found on the best running profile jobs?

How does inboard work with a big fat 1/4 - 1/2 vibration dampening inboard balsa trippler or cheek that's always found on the best running profile jobs?

On the wrong computer to post a photo but guess you haven't seen my Shoestring. You make a channel for the wire tie, on my larger profiles the tank is on the engine side but still held on with wire ties through slots.