+1 I used t nuts ONCE, and would prefer to never use them again. Beyond a pain in my arse. Between tearing out of the wood, and t nuts falling into the box.. soured me on the whole deal
I tried the T nuts as well in my fiberglassed enclosure. I had one in each sub get jammed on me. I had to carefully drill the head off of one of the screws to be able to remove the subs. it was quite scary.