The weak point is the bushed connecting rod in the engine. The connecting rod on any engine has trouble getting enough oil to keep it properly lubricated. But this is mainly at the big end of course as the crankpin rotates inside of it there. So you have to run 20:1 to 25:1 oil ratio in the fuel or you run the risk of the rod failing right there at the big end first.  Unfortunately, NGH didn't use needle bearings in the rod as they couldn't get them at the time. So we need to run more oil in the fuel to help keep the rod lubricated. So do not go light on the oil, maybe put a little extra in just in case.

I do not mind the extra oil residue left over on the plane, it isn't a problem for me to clean off. But I know some people don't like it though. It might be nice to run a 32:1 oil ratio, and the plane would stay more clean like that, but the little engine's connecting rod will very likely fail at this low of a oil ratio.  Now then the rod might hold up OK, I don't know I never tried it, but if the engine went lean in the air for some reason, it would likely cause the rod to fail then with the more lean air fuel mixture resulting in less oil getting to the rod.

The other thing to keep in mind that as the engine gets smaller and smaller, the more oil it needs to stay lubricated. A big large displacement gas engine may do quite fine with a 50:1 oil ratio, but as the engines get smaller then we need to use 32:1 and then 25:1 and 20:1 and so on.