Yeah the plan is a blowthrough, but the idea was to keep it stealthy. I really want a flat response that sounds good, but I also tried to go with as much cone area and wattage as I could to keep some volume. The plan for the front stage is a three way active setup with a dsp for TA/EQ/etc. It doesn't have to be a show stopper since I'm usually riding by myself, but it'd be nice to have a good sounding system for sure!
The port area has definitely been a concern. I've taken into account how much of it will fit inside the box and subtracted that from the volume. For some reason WinISD has no problem showing me port velocity on a ported box, but it will not give me front port velocity on a 4th order, filter on or off. I've searched all over but I can't find an answer for it. I downloaded the most recent version. Without knowing that, I've basically gotten the port as large as I can without having a port that is unrealistically long. From my math the 5x10in port would put me at about 1/3 cone area. I can fit a 5x15in port no problem and be at 1/2 cone area, but I'll have to do some more measuring on the truck to see if I'll end up with the correct amount externally going from the box to the cab.
I've tried to model a ported box that will fit under the seat with the most cone area/wattage that will fit and the SPL seems to be about to same if not a bit less, but it wouldn't be nearly as flat. I've heard to take the SPL graph with a grain of salt as far as what real world numbers you'll achieve, but that the response curve is usually pretty accurate. I appreciate the advice!