If you want perfect eye cup extension length try a Nikon EDG 8x32 or a Zeiss 8x32 FL.Another quick update. The eyecups on the B3 are absurdly easy to remove, and adding a spacer considerably improves viewing comfort for me in terms of eye placement and blackouts. They have regular threading and just twist off counter-clockwise after the stop. I haven't figured out how much width I can get away with yet, but the diameter is about 29.5mm. A black square o-ring would fit right in and look like it came from the factory that way.
I have to say though, I don't understand why so many manufacturers are using eyecups that are just a bit too short in this size of binocular. It's such a common complaint, and it's not like a few mm extra would make any real difference. At least Zeiss actually addressed the issue with the Conquest 8x32.