I once built a 66% scale version of Neil Allen's "Zenith 40", RCM plan #1212. This resulted in a 37 inch wingspan .15 powered pattern style plane that I could take to the field in my compact car without dissasembly. I used 1/16 sheet instead of 3/32 for the D-tube sheeting and ribs and 1/8 inch balsa instead of 3/16 for the fusilage sides. This resulted in a plane that weighed 33 ounces, a little heavy for a .15 but it flew.
If I do this project again, I'll probably power it with a 2100 mAh 3-cell li-po and maybe an e-flite 480 outrunner and strive to get the weight down to the 26 to 28 ounce range, or maybe I'll just buy me a Mini Edge instead.
In retrospect, the scaled down design was way overbuilt for a 37 inch wingspan plane in my opinion. I think 1/16 balsa sheet would be plenty strong for the fusilage sides and the 37 inch wing could have been a twin spar structure with alternating full and half ribs instead of a D-tube and still would have been plenty strong. Also, I could have built the fusilage and wing as one piece since I almost never took the plane apart for transport anyway.

I read in some scientific journal that the reason ants can lift many times their own weight is mostly due to scale effect. Scale an ant's design up to the size of a large mammal and it would be crushed by its own weight.