RT60 and suspended ceilings

Hi Our budget studio is almost complete. Thanks for your help with the plans. We installed a suspended ceiling with a 60x60cm grid for acoustic tiles thinking it needed damping but now the RT60 in the recording area is 0.35s ish empty. I read that 0.5s is the ideal RT60. I have access to 1cm or 2cm rockwool tiles, plaster tiles and a large supply of 20L rockwool bags.We have a 1.2m band of QRD diffusers on a cement wall which remove at least 0.1s, one rough brick wall with large glass window, 2 pined walls and a ceramic floor. The window wall is angled. 87m3 total and 30cm of air gap between cement ceiling and suspended and angled down half way. How should I proceed with measurement and placement of tiles and bags to get the best results? (The QRDs could go in the control room) Is 0.5s the best target? Thanks again GC

Hai GG, Got any pictures? we *love* them :) Did you have a design thread on this forum? if so, please could you point it out to me?

Hi Design thread called "Need Design Help" by GC. Thanks for your help

As you can see we angled the dividing wall as in the plan, but tried to create a zero reflection area in corner 2 and get dense reflections back from the diffused end wall. As the floors here are ceramic we have made the ceiling dead to compensate but would really appreciate some advice on what RT60 to aim at and how to acheive it with Rockwool,plaster,plywood placement in the ceiling, or whatever. Many thanks