As for the other question as to increasing the volume of the enclosure.
Once you determine that the template you have jives with the dimensions you verify and if they don't jive, adjust what required.
Once you got that all sorted out, here's what ya do to figure out how to gain that volume because your going to have to increase depth to gain it with a max width of 44".
Side Profile:
Once you layout the side profile of the enclosure based on the measurements and have included the thickness of the MDF, determine the Square Inches of the Blue & Yellow Sections since this part of the enclosure isn't going to change.
Once you got the Square Inches both, total them up and multiply that number by 42.5 ( interior width of the box ) divide by 1728 which will give you the CU.FT. of those sections.
Now, the Green Section is where math comes into the picture to make up the balance of the volume you need for the rest of the enclosure.
So, determine the remaining Square Inches required for the Green Section to make up for the balance of the volume you need.
Remaining Volume:
Cu.ft. x 1728 = Cu. In. ÷ I.D. Width ÷ I.D Height = I.D. Depth = Green Section