ghetto mcgyver recs on wall panels

so i read rods book. good stuff. then i ran out of money. now i await his new book by one of the following titles. home recording studio: build it ghetto home recording studio: cheap ideas after you're out of money but barring he write those, i have a question. what i have now is a sealed medium room with exposed insulation. see pic. at first the r-19 and r-13 seemed like a good idea. it def cured my flutters and boxiness...perhaps by virtue of it's shear amount it knocked down some standing waves. but now, as was pointed out to me, i have issues with highs. that kraftface is a lot more reflective then my GIK panels. my solution me thinks? find a cheap thin panel-ish material that will absorb above say 4k and put it over a sufficient area. unfortunately the area is at least 800 sqft. one idea i had was to reverse some of the kraftface if possible and cover with cheap fabric. $2/yard. but i'm not sure how well i can fix the kraftface that way. the fabric will probably sag and billow over time.

Once you fill the walls with non-paper back insulation it will sound better. I assume thats not going to happen any time soon? Could yould build a cloud or temporally hang a doona/bed spread over the ceiling.

i think i have an even better idea now. cotton batt insulation is cheap. about .70/sqft or cheaper. it's easy to work with, way less toxic, and supposed to absorb 30% more sound then fiberglass batts. the sound spec is from the manufacturer's website and probably meant from within the wall cavity. bet they do even better uncovered. seems panels and lots of other acoustic absorbers could be made out of this stuff..although no one is doing it yet to my knowledge. it's also mold and fire retardant. treated with a borate compound which is also pretty safe. in fact they even suggest it could be installed raw on the website. seems pretty awesome and it's renewable. the fiberglass shown above has a smell to it. and is a pain to install. another item i came across that may be useful for people like me is a frost blanket for crops. it's super breathable, pretty strong, very very cheap. only issues i see are limited colors (white) and possible gassing out. but i don't know about that for certain. and they are rated for 10 degrees so a thermal insulator as well. i do have 6 traditional acoustic panels and 4 corner traps. so putting up a cloud is a possibility.