Don,
The MM has a good deal of reflex located at the point of attachment, combined with the high location of the insert it will do an 8" Stealth quite well......it takes approx 3 1/2" of stabilizer just to clear the outer edge of the limb pocket.
Either will work, and not throw that bow out of balance(A lot depends upon accessories too)......The 8" will give you a bit more forward stability and soak up a bit more recoil......the 6" will be a bit more compact with only 2 1/2" or so exposed beyond the limb pocket if you want a more tight to the riser set-up. The only thing you'll lose with the 6" is a bit of recoil reduction because its a bit lighter and also some stability.....but you'll still get the same noise and shock reducing benefits tho.
If it was mine I would personally shoot an 8".
Remember Jerry did say on another thread that if you had a problem with balance etc. that he would swap it out with no question.