Bulldog...
I put on a standard touring seat for a Roadking on my 05 SEEG, then drilled the chopped tourpack and installed the backrest from an Ultra that matched the seat.
The standard seat was fine with me, however the better half hated it as it has no padding at all, plus it was very narrow. (no comment on that one)
In any event, the setup is perfect for her now and as long as momma is happy, life is good.
Tom