Jon, a shim like that tightens the seal twice as much at the parting line as at the top and bottom. I guess that's all right since the seal lip is flexible, but it's why adjusting bearing clearance is done with a tapered shim- - - -twice as thick in the middle than at the ends.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!