Installation of diffusor (fruit crates)

Hi, i got few pieces of fruit crates (similar to egg crates) as diffusors on front wall (trial & error), i have tried double-sided tape but the installation of crates to the wall is not secured.

I am searching for adhesive instead to fix at the back of crate (4 sides). May i know what the best recommended adhesive available which is not too strong until the paint to be peeled off? Easily to be sought in bookshop ?

Cheers

Just bought 'Bluetak' reuseable adhesive, hope it would work for the crates.

Does a listening room need to be absolutely 'dead' with no reverberation? It may sound like when you play a boombox on a beach. Horribly flat. Concert halls and Bose tech needs walls and reverb to work as intended. Perhaps our listening rooms need not have too much of this unless we have large wooden cabinet panels, etc. which are vibrating and causing trouble?