That seems to be a good capstone to this inquiry. The SSSC as an Experimental seems to be an optimal trade off between performance and sufficiency ruggedness for safe daily operations. The Limit for VW appears to be the 1/2VW only to free up enough weight for proper structures.It may be possible, but it's a very slippery slope towards a disaster. With an engine that is heavy, you will be forced to look around for other places to remove weight, like the spar caps, longerons, and landing gear. We've all seen Part 103 legal airplanes with microscopic little wheels that look ridiculous. That's the best case scenario, to have an airplane limited to smooth pavement. The worst case is that you took too much weight out of the structure, and you have something that is not safe to withstand a 2 or 3G gust.
All thatis for a conventional airplane. If you really really want a heavy engine on a Part 103 UL, then the safest way IMHO is a powered parachute using a real light aluminum tube buggy. The "wing" on the PPC weighs very little of course, so you have a good chance to make 103 weight with a heavy engine.