Here's a suggestion- - - -how about adding a thin piece of shim stock between the lip seal and the block and cap after trimming the shim so the seal ends can meet? For instance, if the shim between the block and cap is .002", cut a piece of .001" stock the width of the seal, and lay it in the groove in the block and the cap before installing the seal. The ends of the seal will meet, and the pressure on the crank hub will be the same as if the shim was not there. When adjusting clearance on stovebolt rods and mains, I never use pre-made shims, I just cut my own from a big roll of shim stock I've had for years. The same stuff could be used for shimming the fit on a lip seal.
Jerry
