The seal should have come with instructions --- and you should follow them as exactly as you possibly can. When I did mine, the instructions said to seat the seal fully into the groove (cap and block) then carefully trim the ends so that they protrude above the mating surface exactly 1/32" -- and be careful to make the cuts smooth and square. For final assembly fill the 'holes' in the groove with silicone sealant, put a skim coat of sealant on the ends of the seal where you trimmed it, install, torque, and let it sit for 24 hours. You should do this only when you're ready for the crank to go in and stay in because you don't want to disturb the seal after it's installed.
I did all that on my 461 - to the letter - and it still leaks
I'm guessing that most of the reason is because I also had my block align honed, and that process results in the seal groove being slightly egg-shaped instead of round. If I "get around" to re-doing it, the next time I'm going to use one of the graphite-impregnated rope seals.