What sound deadening material for inside my LCR box’s (not stuffing)? Box resonance.

I have some 2-way 12” with a cd / horn LCR speakers that I DIY’d that I believe have a terrible resonance due to the dimensions of the box and the 3/4” MDF board (bracing too).

I would like to put some kind of dynamat adhesive mat and some egg crate foam type stuff behind the drivers AND still put some stuffing back in, what do you guys recommend for doing this?