the fz6 cup seat has my vote 80%
my wife wont pillion on a bike, she prefers to ride it
i wont allow my kids on the back and if pillions were an issue i would buy a cruiser or tourer and keep the fz6 1up only
but thats just me
i emailed the fz6 cup manufacturer after reading in a local mag about the company, i will try to find thier details when i can, but i think it was $360AUD + postage (they are on the other side of AU to me) so not bad price but then factor in fitting (will be some trimming i was told), painting, wiring depending on the lights you choose (also affects cutting), making your own seat (you will need to make your own cushion, no one will make one that off the shelf as a replacement and i think its a flat fibregalss base under the seat, so its stick on style) and then also your missing your underseat storage (not much there anyway)
and to finally add to the list... removing (cutting more likely) the pillion pegs off to keep it looking clean
hey you might be best to grab that seat cover after all and mod your seat
on another note, the r1, r6, fz1, rgv, etc etc tails will fit, some need a new subframe welded up (not that hard if your a techy sort and not that expensive to get a fab shop to make) or in old subframe modified to fit.
i think after watching a mate sort out an 06 r1 tail onto his honda cbr600f it should be fairly straight forward, his cbr also had the banana style seat and he hated it.
a whole weekend with the angle grinder and welder and he had a frame attached the next weekend the tail was added and then during the week he modded the attachments to fit the seat.
ill go to a fab shop i think