I built mine from 16mm plywood and it's a very tight fit for the sub. I think you would be very happy with just one 13TW5. I will try and post my box dimensions in the next few days but i been so busy this week i aint had a chance.

I love your setup!! I was looking at the JL 13TW5's also. Their website says they are 12.96" and need .80cuft to sound good. I am going to build box myself. I'm assuming that it's an 09 screw. I did some rough measurements, and it seems that it would stick out a little if I use 3/4" mdf. Did your guy use 3/4"? Also, wife has me on a tight budget. Would 1 tw5 still sound good with a JL 500/1v2?