I "only" have a 29.5" draw, and I shoot split finger, so I don't ever listen to my Shrews under the conditions you have with a 30.5" draw and three under, but my Shrews are all quiet with cat whiskers on them, and not too bad without any silencers. The 60" Shrew Safari that my friend just got is super quiet without any silencers at all, and he has a 30.5" draw also. But he does shoot split finger. My Shrews are generally braced at 7.25 to 7.5 inches, but I have shot them at 8" with no problem. I suggest a high nock position and a high brace height as the direction to head with what you have described. The suggestion of an 11 gpp arrow or heavier might also be a big help. The other guys here have made the best suggestions I can think of, other than having you join us split finger shooters. :D
Allan