Depends on what mount you use. I've used "store bought" mounts and made my own at times. But to answer your question, Yes, a different mount could change everything, to the bad or to the good. Before they came up with the bolt on mount for the OCC's I was welding in my own cross brace as I'm sure a lot of guy's were doing. Moto is right in theory, the chain alighnment should be PERFECT. But in practice it can be off VERY, VERY LITTLE and still ride the sprocket. (ya notice I said VERY, VERY LITTLE.) Perhaps a thin washers worth. Sometimes this is just enough to keep the chain off your tire. Of course perfect is recomended, but if I were going for perfect I wouldn't use some cheap thing that came out of China.
I was just looking at yer bike in the gallery. Is that a 24" bike or are you just a BIG DUDE. The bike is great by the way. Nice job.
Big Red.