Well I did post a picture of the cover. And the "plug" on the picture cudaboy posted was on the cover. So I think got that "covered"
This forum is very helpful most of the time but sometimes it feels like some things are beeing overlooked (by myself as well). Combined with my english skills, things are getting confusing.
I try to make some pictures from the side and front. I think my exhaust will be in the way. But I'll get it done.
Maybe it is just a normal 8 1/4 (why shouldn't it) with a perfekt round cover, which jut out the flat bottom. The only thing that bothers me with that theory is, that the screw should be higher.