I own a cutter. It has the 51’ mast. The manufacturer moved the position of the mast aft as you said about 2 1/2’ vs the ketch and sloop. That includes repositioning the chainplates. The
interior of the cutter had 2 layouts, one the same as the ketch/sloop, one quite different which does not have the forward entry.
I have been all three versions and know an owner that owned both, first the ketch then sloop. The sloop has a longer boom, that’s it.
All three versions are from the same
mold, top and bottom. The sole of my cutter has the reinforcement for the mizen mast.
Check out pearson424.org or the facebook group for good info.