From a thickness perspective, 50 to 100 Hz is impossible to treat through material. There are other ways you can build tuned traps which can be used. But in the 50 Hz to 100 Hz, PEQ is better. In my case (read my thread), I had a very strong mode at 34Hz which didnt budge with any bass trap but was easily handled by PEQ.
Tuned Bass Traps are slightly more difficult to DIY, there are ready ones from GIK but you can buy a PEQ at the same price.