It depends a lot on how important "scale" flight is to you. The other day I was flying my DC-3 when a real DC-3 flew over. Looking at them both in the the sky together it was clear that mine appeared to fly several times faster. A real DC-3 looks like its floating along! Now mine is 60" WS and about 17 oz/sqft which is pretty good for a twin. It's fiberglass covered foam and has maybe 150 flights on it. It has withstood tremendous abuse and other than rebuilding the landing gear a few times I've yet to break it. If I had a DC-3 designed by say, Pat Trittle, it might have 1/2 the wing loading or less. It would fly at a much more scale like speed.
However, I doubt it would still be in one piece the way I fly and where I fly. Also, I routinely fly mine in winds of 15mph with no problems. A lightly loaded plane is more affected by turbulence. So it depends on what you are looking for in a plane. Lightly built stick and tissue planes do look more "scale" in flight but they don't look scale when they are buffeted by turbulence. They are less crash resistant too. So I fly those in calm winds in a nice scale like pattern.
The plane that you describe could probably gain 20-25% in weight and still be a nice airplane to fly. I'd beef up the areas that broke first on similar planes. No sense beefing up structure that doesn't need it.
They say build to fly, not to crash but want my planes to last as long as it took to build them.....