The space thing was a real concern for me, too. I'm operating within pretty tight constraints on a 27'. That said, the 44" spectra CHE membrane that I managed to squeeze in there was one of the best things I've done, and I consider it one of the best uses of space on the boat. Having excellent quality water
from a proven and highly efficient WM that only runs a few hours every couple days is, IMO, simply fing awesome. If you can somehow find a way to fit a larger one I doubt you will be disappointed.
I had to cut out and re-build a bulkhead under the settee to get it to fit. But looking back on it now, it was a small price