This is the only first hand report on this subject that I have read on either of the two motorized bike forums. It comes from a builder down in San Diego who runs the Honda GXH50 without shrouding:
"I took the sheet metal off straight away. That was before reading all the warnings in the other thread. I did get a good thumping from the flywheel on my right index finger trying to turn the pull start handle while riding. OUCH! I stopped at 7-11 for a band-aid. The lady at the register asked me if I would trade the bike for her truck. LOL.. Other than that - nothing that is noticable. When it gets over 100 here I'm usually headed to the coast looking for a breeze. I don't ever sit in traffic as this bike is only for fun. So the sheet metal may help in those instances, but I avoid high heat & traffic. It does seem stronger on a cool evening ride....."
The photo attached is of the bike/set-up by zombybuilder
ocscully