tailspnr,
are you sure you need shorter standoffs? Do you have the Cap yet. I think DA sells them +/- 1/2", but better answer would come directly from DA. Any other stand-offs would be just fine too. I had a DA50 in a DiablotinXL. I decided to cut the firewall of and move it back to where by lengthening the stand-offs by about 1-1/2" the carburetor would breathe fine without a hole in the firewall. I would have had to do something to the firewall anyways, since the engine stuck out to far. Once you realize that you HAVE to cut into that nice new virgin ARF, even one from Chip Hyde ha ha, it is easy to mount these engines with rear carb., just think thrice, measure twice, and cut once he he. Good luck with the Cap, should be an awesome 3D machine.
DKjens