Doing a cut-thru, 6 SA12's - 4th order or ported? Birch or 1" MDF

[5K Mobile Electronics]

So, as the title says, I'm doing this cut thru and need some suggestions. First I need to know about the wood. I'm new to building with birch, I just called my wood wholesaler and asked about what birch they had(sizes and ply count), they stock 9 ply, but says its a veneer core, not birch all the way through? It was about $30 more than what I pay at Home Depot or Lowes for 5 ply. My question is: is all birch this way? as in birch only on the faces? Second question, should I double layer 3/4 birch for the enclosure, or just go single 1" MDF for the whole thing? And then on the enclosure design itself, I was looking at doing 3 on each side with a port at the back of each side, sealed up to the cut thru, but it actually looks like I'd take up less room doing a 4th order in there? The truck is a 2010 ext cab Silverado with a full size cap on it. Here is a rough sketch of the ported enclosure I was thinking about, but will this turn into an unintensional 6th order?

[412 CVX]

Most people do 4th orders for blow through boxes. from the way your sketch looks, that's probably going to end up being an improperly tuned 6th order. and you probably don't have quite enough room to do a properly tuned 6th order without taking up the entire truck bed.

a 4th order would definitely take up less room. although if you really wanted to do a 6th order it might be possible. i'd have to know just how much room you have to confirm this though.