Yeah been thinking over the weekend and the BH is probably way too big for practical use so gonna concentrate on the smaller 215B. This one here or one on the left up above. Have tracked down most of the dimensions now. Just need to know the port width at the back where it stops or if it's a perfect triangle if it continued to the back of the cab.
"Internal dimensions:
38" high
12" deep
22" wide
38 x 12 x 22 = 10032 volume.
The port size is:
38” high
10” deep
6” wide
38 x 10 x 6 = 2280/2 (since it’s a triangle shaped port) = 1140 volume.
So the cab’s internal volume - the port volume = 8892 volume"