Box for two Sundown ZV5 15s

[Slavis]

Hello. I was hoping someone who has some more experience than I do with building boxes could point me in the right direction. Im trying to build a box for two 15 inch Sundown Audio ZV5's. The amp powering them in a sundown sfb-8000d. I went on sundowns website and they do have a box build however it is just for 1 sub and I would prefer one box rather than two seperate boxes. I would like to build it as close to the recommended specs as I can. I drive a Tahoe and I took out the third row seats so I do have a good amount of room for the box. The exact dimensions are 48 inches wide, 37 inches long, and up to 20 inches tall. My first question is should I make the box that big? I have never built a box in my life and to be honest I have no idea what Im doing when it comes to the determining the size of the box or what size I should make the port. I tried to download torres calculator but was unable to complete it because I didnt know what to put in for the dimensions. I have five 49 x 97 MDF panels that are 3/4 inch thick, I would assume that should be enough to build the box. Ive got all the tools I would need and Im pretty good at building things but as you can tell not good at determining the size of of the materials I will need. If someone can point me in the right direction maybe to a program that can determine the sizes I need I would really appreciate it. Or if someone is interested and has some free time I would be willing to pay for a blueprint of the box that shows me the dimensions of the pieces I will need to cut and where they go to put it all together. Id prefer to pay in bitcoin but if you want google pay or cash app thats fine too. Thanks