That mount needs to be trimmed. The stock mount is open on the back lower end. Take a look at an original frame and you'll understand what I'm talking about, sorry I don't have a picture handy for you. Once you do that, you'll have clearence for your cover and still have a solid tank mount.
OK, so it bugged me until I went out, dug to the back of my pile, laid on my side, lifted the dust cover, pulled the half mounted tank back, and from a angle I can't describe, took this shot of the lower tank mount. Hope helps. I have a similar motor, that will be going into this frame, and it has STD heads too. Just to lazy to drop it in for the photo. Not to mention the other bikes in front, and all the boxes of parts, mumble, mumble, mumble. Ok, I am going back to work.