I don't worry much about engine weight. As long as it's strong for it's weight I'm usually happy. I'm going to put it on a stand before I commit it to a plane. I've watched some YouTube video and nobody seemed to have any problems with it and I haven't seen anything online saying it has problems.
Does your carb close all the way? Mine is open about 1/16". If I back out the throttle stop screw any farther then it completely lets go of the barrel and it can start spinning around. I've never seen a carb like that before. Every other engine with that kind of carb design allows the carb to completely close while still having the screw in far enough to hold the barrel in. The screw has to turn out several more turns before it lets loose, but not this one.
I always set up engines so I can shut them down from the transmitter but I'm concerned this design might not allow this.