You can make a small bracket with two holes the same size as the rear mount hole, next to each other. Remove the rubber grommet from the rear mount, attach the bracket to the rear mount with a nut and bolt, insert the grommet in the other hole in the bracket and insert the bearclaw spike through the grommet, thus moving the rear of the bearclaw out a bit.
That's what I did before I cut the bearclaw. It does leave a gap between the bearclaw and the tank, but its only really noticeable from above.