I've built up a MDF box w/biscuts & tightbond wood glue, cut out all the holes, & put in two sets of 1"x2" popular cross braces above and below the bass baffle, each set has one brace to the left / right panels the other being attached to it and the front / rear panels, and I've got my pi kits ready to install.

1) It seems pretty solid right now, do I need more bracing? For example do I need to put anything on the top bottom panel centers?

2) Time to make it air tight. What do you guys recommend to seal the insides of the mdf panel corners? How about pl-400 or one of those window sealers? What have you guys used successfully?

3) What do you recommend I seal all the removeable parts with?

4) What is a good way to mount all the electronics in the box, worried about vibrations...

5) What is the best way to attach the r13 to the mdf.