I always stick to the 1 1:6 2:3 rule, then it doesn't really matter how wide it is. I would definitely do a prototype and see if it works there. I tried my sub under my tv and the LFE messed with the sound coming from the center channel. Had to move it. Ended up going with 2 subs, 1 in each of the front corners. Sounds wonderful now. Nothing worse than spending lots of time and money just to find out it sucks
Well it's quite easy, lets make the cab 1ft deep, then we would make the height 1.6ft and the width 2.3ft. The ratio given is to help eliminate standing waves inside the enclosure. There are other ratios that do the same thing. The point is you were worried how wide you could make your cab before it started effecting your sound. Using this ratio and aiming for a Qtc of .707 you will be well on your way to having a great sounding sub.
Sorry, I just noticed a finger problem in my response. The ratio is 1:1.6:2.3 (had the colons in the wrong place). So using your given space you could put 2 cabs of 16x 25.6x 36.8. If you were using 3/4" MDF that would give you 2 cabs with 7.13cuft each internally. If using 1" material internal space would be 6.65. After adding bracing you could drop a Dayton 15" titanic into each cab and have a Qtc very close to .707 as the Titanics have a large Vas of 5.46.
2 x 6,6ft3 that sounds nice, now im gonna start looking at drivers. I want sealed with a q of around 0,6 also want something more sensitive than the titannic, and dont need 20hz at all. my ht is only L 10,5f x w7,2f x H8,3f so its almost impossible to get a good bass that low down. good extension to 35 is fine with me.