An 8-round 9mm cylinder is 1.71" diameter, which is N-frame territory.
By contrast, a 7-round cylinder is 1.56"
A 6-round cylinder is 1.45".
A 5-round cylinder is 1.31"
I would prefer a 6 shot cylinder over a 5. I don’t know if I would go as far as an 8-round
The cylinder -could- be reduced in length considerably (vs the usual 1.73 - the 9mm could lop off 1/2") but to make an abbreviated gun will require a frame/yoke/trigger design dedicated to support the short cylinder if this were to go from conceptual to functional or very little has been gained.
And there is still the nuisance of moon-clips vs the somewhat inconsistent extractor groove diameter found on 9mm brass; even within the same brand sometimes.
As mentioned previously, the lack of a roll crimp on the 9mm means that bullet creep in a carry-weight revolver is non-trivial. It could be a stoppage issue with a cylinder that is barely longer than the COL of the 9mm.