don't feel bad I had the same problem and never figured it out and went and got a seal with a smaller inside. yep 30,000 miles and it is leaking again.
with this info I may try again.
I also tried not seating the seal all the way. figured new area. nope, it spun out of the block, front oil seal on a Mazda pickup.
oh this is on an arrons rebuilt motor, from I guess mexico as the addy was in tex. I found the first time it blew that they used the cam seal on the crank..... yes it fits.