Inside the body of your r/c truck(s) where the top roll bar would be, bend a tube of aluminum to fit. then pad the ends with foam and put zip ties around them. Next drill two holes through the lexan and the tube where you could put a bolt through and put two "rabbit ear" or "wing" nuts on them. it helps A LOT!

tip from Clayton....   picture example

After cutting out the wheel arches I use a round can,slightly smaller than the cut-out,usually a spray paint can,wrap a fine or medium sand paper around the can and use it in a rotating motion to put a nice smooth finish on the arch.I also put a radius where the arch meets the bottom of the body so as there are no sharp corners to catch on trackside objects or marshalls.

From: Paul Watkins in Toowoomba,Queensland,Australia. 

Color shifting paint: After the standard wipedown of the inside of the lexan, I started with a light coat of candy purple. It's a bit of a challenge to get it even, you should be in a very well lit area. Just hold it up to the light, any flaws will be evident. You will need to shoot the second color while the first is still fresh...within a minute or two. For the second color I chose metallic burgandy. This should be a heavy coat, not so heavy it runs of course, but heavy enough to be sure it bonds with the undercoat of candy purple. I have also done the paint with candy red followed by silver, and cancy blue backed by metal flake black. All produced the same result. An eye catching paint job with no more maskin than the windows...less if you race nitro cars (I usally remove the side and rear glass).

From: Rich Dixon in Lemon Grove, CA.

You can see both his cars on page 19

These are known lexan artists that I have come across, if you want to leave the work to them.