Need Input for Box Design

[Dirtydodgeon22s]

Hey all, new here to the forum but not all that new to the stereo scene. I'm looking for input on a box design for my single cab Dodge Ram pickup. I have 2 JL 13w3s powered by one Kicker 1500.1 and was looking to build a down face enclosure that would measure right at 14 inches at the bottom with a solid back wall and slant front, the trick is I was wanting to port it as low as possible but still keep it all behind the seat and below the rear glass line. My questions are these:

How large should I go volume-wise for these two subs?

Is there any problem with using a large round port stemming from the side of the enclosure? Meaning it will not be on the same face or on the opposite side of the box from the woofers but rather to it's side at a 90 degree angle.

Any input would be helpful, thanks guys