Dear forum,

I plan to treat my room with bass traps. For cost reasons and fun, I would like to build them on my own. However, I would appreciate your opinion on the design I have in mind, so that I don't waste my money

Requirements:
Priority 1: prevent potential health disadvantages of certain materials (despite the certificates...)
Priority 2: effectively absorb low frequencies (50-250 Hz)
Priority 3: also absorb some mid and high frequencies (250-5000)
Priority 4: price / design

Design:
My idea was to build a right-angled triangle bass traps (both sides of the triangle being 70 cm and the hight in the middle of the triangle being roughly 50 cm).

It should be a panel absorber with a thin membrane out of plywood or MDF, filled with multiple layers:

1. Layer: At the back, I want to use a 30 cm thick layer of Rockwool Sonorock, wrapped in 0,3 mm thick Polyethylene (PE) foil, knowing that this will give me more reflections (but mostly in the mids and highs). For that reason, I want to add another layer of insulation:
2. Layer: After the Rockwool, I want to use a 10 cm thick Basotec layer
3. Layer: 9 cm air gap
4. Layer: 10 mm plywood (membrane)


So, my questions are:
1) Does this layering make sense to you in general?
2) Would a quadratic shape be better than the triangle shape (assuming space would not be an issue) due to more volume and if yes, where would I add the membrane? Only on one side?
3) How exactly would I actually add the membrane and what do I need to take care of to ensure prober functionality of it?
4) What air gap size and membrane thinkness would you recommend?

I know its a lot of questions, but I'm happy for every piece of information. Thank you so much in advance!