In 1/72, it's likely down to how the kit hull is constructed.
Juggling a cut plug (two seams) might be easier at the smaller scale. Depending oun how a cut plug cam out of the donor, naturally.
The cut wants to be just forward of the aft end of the well, with appreciation of just wher a person will be comfortable with putty and sanding.
In larger scales, I'm pretty sure I'd do it as a single cut on two kits. Strike a line on both kits about four scale feet from the aft well bulkhead on both. This line ought be adjust ed to presecerve deck & other moulded details. Cut the after portion three feet forward of the line; cut the donor three feet aft. Then join the two.
The remaining halves could be made up as one of the many iterations of dive/work boat, or ramped lighter, seen about the maritime world. Such craft have the helm position removed to be replaced with a cabin (or a shanty house) structure.
Toughest part is with modeling how crudely such craft are built, what with obvious weld seams, rickety wood cabins and the like.