I bought a can( 1 pint) of mineral spirits to use on the side seals, I use a 5 CC hyperdermintg(SP?) syringe(buy them at the local drugstore or animal feed stores) and needle to squirt the mineral spirits down the sides of the seals after there installed(with the motor upside down on a engine stand) I also use adhesive silicone RTV to seal the seal holder up to the rear of the block rear main seal sides totally on both sides after letting the mineral spirits soak in overnight As far as drilling or grinding a slot on the seal holder I don't see any need for that The seal is sealing against the crankshaft and the bottom of the rear seal holder and the lip on the seal holder is probally (I haven't measured it exactly ) .100 or more away from the crankshaft rear main seal surface so there shouldn't be a issue with the lip holding more oil against the seal than can drain out by gravity I do lube the seal lip and the crankshaft with high temp moly grease so it won't be torn up while degreeing the cam and other times rotating the crankshaft around before starting the motor up the first time Don't forget to prime the oil pump while turning the motor over before starting a new motor