Dual layer drywall question

Hey folks, just mudding and taping the first layer of 1/2" sheetrock on my garage walls and i have a question about optimum sound reduction.

First a breakdown of the wall assembly.

Outer wall: original real dimension
2" × 4" with 2" styro board inset flush to 1" barnboard on the outside

Inner wall: floating 2×4 fastened at bottom to foundation and at top to ceiling joists with vibration absorbers separated from outer wall by 1/2" airspace. Inner wall does not actually touch any other outer assembly.
R22 5.5" fiberglass pink filled between both cavities.
6 mil poly vapour barrier tacked on face of inner wall sealed with acoustical sealant and blue tuck tape.
Some joints further sealed with Owens corning JointSealR 4" tape.
All staples sealed with blue tuck tape and bottom of poly sealed to concrete floor w acoustical sealant and JointSealR tape.
2-3 layers of Alcan heavy duty alum foil covering all 6 mil poly.
Bailey RC Plus resilient channel on 24" horizontal centers top to bottom on walls and ceiling fastened at 16" centers on studs with dual layer 1/16" rubber squares and then a 4" x1.5" piece of very sticky Resisto bitumen rubber folded in half and wrapped around the screwing edge of the RC Plus and screwed through to the studs.
1/2" drywall/sheetrock screwed into the RCPlus with 3/4" #6 cabinet screws so as not to pierce the vapour barrier.
All drywall joints sealed with mud and paper tape.

OK, so would it be a better idea to use some drywall mud in small dollops between the first 1/2" sheet and the second 5/8" firecode drywall to help both sheets act as a single mass....
or not and let them vibrate independently.
Which would provide better sound attenuation across the spectrum?, from those in the know.
 
After the paper layers absorbs the moisture and the mud drys hard you might create outer edges that will breakoff and vibrate since you will not completely squeeze flat the mud in the
Particular scenario you mention.
Use a panel adhesive or thin foam that will always stay somewhat compliant and at the same time absorb and displace the large area panel vibrations.