I think I have sinned. Absolution anyone?
I've covered the front wall in 4.5cm (2'') 22kg/sq.m mineral wool (realised later how low the density was). This to secure and stop rattles and equalize a little between both sides, because almost half of that wall is taken up by a huge old window (gap filled in with drywall). Room is for general tracking and some solo vocal recording in live end. At a puny 5000 Pa.s/m2, I realise that this is probably sonically worse (steep ramp below 2khz) than if I had used the lightest fabric available or vinyl, to sort the rattles only. Unfortunately, I am forced to start measuring after I have got these reused materials up and out of the way (not that this aspect will be measured).
Cannot go back now so what would be the best cure for a better starting point for this room? Another layer of much denser wool hung in front with an air gap (better cure for window asymmetry)? Cover the existing light wool with a thin vinyl tarpaulin (I have one) and a few more 4'' 705 traps? Or cling film then hang large flat 2cm (1/2'')-thick melamine panels (have some and slats too complicated for this project level) in 50% of area plus a few more 4'' 705 traps? Any help much appreciated.