It is kind of funny that no one even raises an eyebrow when larger than recommended engines are installed in RV-4, -6, -7, and -8's.
I guess only the -9 will fall out of the sky when over engined.
One thing to keep in mind, and we in the RV world often forget this. The O-320 150 hp Lycoming was designed to lift a four place engine. In our little planes, they are a great choice, if you keep everything light.
When I had the O-290 of all of 135 hp in my RV, it was a GREAT combination. When I would travel with the local RV gang for a couple of hundred mile trip, I would take off first and when I would enter the pattern, the last airplane ahead of me would be just touching down.
The bigger engines really only gain you in ROC and not so much in cruise speed. Even then, 1400 FPM is nothing to shack a stick at.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC