Help with box for Fosgate power hx2 12

[Souldrop]

Well waiting on a recone kit for a power hx2: rfr-3112 I recently purchased...in the mean time I'm going to go ahead and design and build the box. Are there any suggestions as far as tuning or size? I have roughly 16"x30"x20" to play with in the trunk of a 95 avalon. It will be run off a T1000-bdcp @ 4 ohms. I listen to most types of music (Rock, country, rap, and techno to state specific genres). I was going to go with the suggested box at 2.5 cubes tuned to 40Hz but want to see if anyone else had any other/better suggestions. If not I will just use the suggested box size and tuning.