I have an aluminum frame Hybrid 21-speed (Trek) with a Honda GXH50cc driving a Staton inside drive gear box mounted behind the seat as seen in the photos above. It also sports the HD clutch assembly. Only I built my own mounting hardware instead of using the provided parts. It's a really nice set up if you de-govern the engine after the break-in procedure. I remounted the fuel tank over the gear box to lower the profile. I made careful not to mount it lower than the carb fuel inlet, to maintain proper gravity fuel feed to the float chamber on the carb. Looks cool. It has been reliable in my case since the beginning. I would say the Staton offerings are pretty good. It lives up to my expectations to the point I now have to consider a braking system upgrade.
The only real work to perform is regular spoke adjustments (2 to 5 usually loosen up a tad) after each run and a drive chain tension-check and adjust. I Loc-Tited all the bolts during assembly along with installing Heli-Coils into the tapped holes that were drilled for the installation procedure. So everything has seemed to remained tight so far.
Can you place photo of your bicycle?