Thanks Wayne, looks like I'm going with 3/4" MDF since that's what's available and reasonably priced in my area so I will adjust the port size accordingly.
Theres no specific location for the terminal plate on the plans, I'm assuming it can go a couple times inches below the 2nd braces below the woofer?
Also, where do people usually mount the crossover? And is there a preferred method to mount it?