[hharney]

The Super Skymaster with TSIO-520 rated at 310 hp has the same structural limitations as the standard 337 airframe that it was modified from. The advantages of the increased hp is climb. The higher speed at altitude is true airspeed but the calibrated airspeed is still within structural limits. The Super is about 20-25 kt faster at altitude with a cruise of about 220 kt TAS. The positive was 2500 FPM climb but the extra weight of the engines eroded the useful load terribly.

The 73 and newer airframes were substantially different from the pre-73 models. Cessna also changed the wing spar in the H model vs the G model. There were gross wgt increase mods but all landing weight requirements remained the same except for some proprietary STC's. I am not aware of anyone attempting to increase the structural load limits. It would be very expensive (if any possible) and there just isn't enough of an audience to justify it.