I had a similar question a while ago, but now I actually have corners available I can use, and I still haven't built the 4Pi's, so now I'm ready to build 7Pi's.

Unfortunately, I still have a height restriction due to a windowsill(and WAF as well). Ideally around 26" would be good, but 28" is doable as well.

I'd like to make the cabinet shorter and deeper. Obviously the box volume and port need to be kept the same. However, I don't know about the importance of the height and the rear volume. If that can't be changed, It seems I'm probably out of luck and I'd have to build the 4Pi's.

I'd also like to build a cabinet thats trapezoidal, so its 24" at the front to match the midhorn, but I realize that may negatively effect the mouth of the horn.

If you have no idea how all these changes will work, I'm willing to build a woofer cabinet and see how it works out and make some simple measurements with a RS SPL meter.