I installed my Vortex flash suppressor after getting in a new crush washer.  I previously had a peel washer on the threads, and still the Vortex was bottoming out.  The threads were still showing after Vortex was screwed on tight.  So I decided to add the crush washer infront of (on top of) the peel washer to shim the threads so that my Vortex would go on nice and tight and there would be no exposed threads.  Is this setup alright?  

Sounds OK IMHO. Some people use the old style lock washer from the A1 birdcage if they're not worried about indexing. An innovative idea that I've seen used is to take a 1/2in. helicoil thread insert (if that's your size) and use a Dremel with a cut off wheel to remove a thread or two to use as a shim or spacer between your Vortex and the barrel. Taper the cutoff ends using a stone on your Dremel. Use a larger size helicoil insert if you have an HBAR or bull barrel. The helicoil is stainless, so no worry about rust. It works, and provides a nice finished (professional) looking job.

I know that, but with just the crush washer there are still exposed threads.  It needs the extra shim from that peel washer and vice versa.