In the AKA instuctions, they have a unique approach...
They have you build a holder out of two blocks of wood. I clamped the blocks in a vise and drilled a hole slightly smaller than the reg body straight through on the seam so that 1/2 of a hole was on each side of the blocks. I've made two of these sets, one large and one small. I've used these over and over on all sorts of regs to clamp and firmly hold in a vise with no scratches.
Thats just me though!
Exercise your constitutional rights, but keep your laws of of mine.