Back to the original question about protruding transoms on RC boats. The OSSI gas tunnel came with a transom set behind the sponson rear by almost two inches, and also has a butt load of negative thrust angle built into it. I am sure the designer did a copy of some full scale hull as you refer to. The design was really bad for RC use however, lead to hooking and spinouts even when you used an adjustable mount to eliminate most of the negative thrust. The full scale powerplants are much more compact than our RC lower units resulting in the prop being closer to the sponson rear in the full scale boats. Add the prop distance of a lawless or other gas lower unt and the thrust angle is way to far rearward, ergo pushing the *** end of the hull around the first time you overload the ability of the sponson to hold the water in a turn. BLUF, keep you transom design in a position that places your pivot pin close to the line across the rear ends of the sponsons. Most of us cut the extended transom off of our OSSIs and moved it forward.
