Shim option - cut out of alum pop can, slightly undersized to the base (don't want it hanging out the sides but must make even contact) and holes drilled for taps. Place under the rear base and tighten down as per norm. .010" thickness will give you approx 7" more elevation.

Of course the other option is different mounts.

Is it possible the rings were inverted (some are front and rear specific)???