I do wish the Fujiyamas came with eye cups or guards!
I used to think that too. My 6mm Fujiyama is the oddball of my eyepiece set in that it is the only one without an eye guard. And I'm a "contact" observer - I like to have part of my head in contact with the eyepiece versus hovering. I've always been that way.
However, I find with the 6mm Fujiyama that it's not a problem - I tend to put the upper part of my orbital bone (???) in contact with the edge of the eyepiece top and it just works wonderfully. I would not be able to do that with a volcano top. I've used the Fujiyama likely over 100 times now, and I've never sat back and wished it had an eye guard.
To each their own, tho - I know I'm "special" (cause Mama always told me that!).