Good idea- - - -I'm also planning to taper the ends of the washer at the parting line where the cap meets the block, to give the washer some hydrodynamic lubrication from the crankshaft rotation. The countersunk Allen screw heads will also trap a little oil, as they will be recessed a few thousandths below the contact surfaces. That's also why it's important to chamfer the crankshaft oil galleries a bit where they intersect the boundary layer at the rod and main bearings.
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!