Hmm .. I don't have the eibach spacers so not sure but I would have someone check them out or call eibach. I wouldn't think there's supposed to be any gap.

It almost sounds like what you're describing is like using incorrect sized hub rings that are keeping the wheels from seating flush with the spacer. At least, if I'm understanding you correctly. Are you using hub rings?

Wait a sec. Are you saying the HEAD of the original bolts stick past the spacer 1-2mm - therefore keeping the wheel from seating on the spacer flush? Then in that case I would say that's a problem. The bolts you use to mount the spacer should not stick out past the spacer.