Bill, I would go with Brackish's recommendation of just jacking up the keel fore/aft when the time is right to paint underneath the rollers.
I just tie lines from aft trailer frame up to jib sheet cleats to stabilize it before dropping the bunk boards, clean/prep/paint everything in sight, then jack it up, clean/prep/paint under rollers then reinstall bunks once paint is dry. I have also done under the rollers first, then the rest of the boat..either way works.
FYI, I've found that a good sized drill chuck will fit the end of the scissor jack rod. Cranks her right up and very quickly to boot.
Since we're neighbors and all, if you need a place in the grass to paint (or borrow the scissor jacks/jackstands, I have several of them I kept from old cars), lemme know, you're welcome to either/both.