I had the very same concern while building one from a kit that I powered with the 46FX. I got nervous as there's some heavy construction involved! I ended up putting an UltraThrust muffler on the FX to give it an extra boost. After flying it for two seasons I don't think it really needed the extra 1,000 rpm the muffler provides. The Seamaster is just one of those planes that does not know that it's overweight.

Rich