Gentlemen, this is simple stuff. I, too, found the stock seat on my '06 (same seat as the 1250) somewhat harder than an ironing board with my boney butt on it. Sooooo.....I went to my local upholstery guruess, she sent me off to her foam supplier, I tried out a variety of densities by sitting on them in their warehouse, picked what I thought would do the job and then notified the guruess.
She took my seat, unstapled the cover, shaved the stock foam down by exactly one-half, glued on a block of the stuff I'd selected at the foam supplier's, shaped it properly, stapled the cover back on and gave it back to me. All for C$50.00......and now I can go for about 2-3 hours without numb-butt.....instead of the 20 minutes with the stock setup.
Plus the seat still LOOKS stock and everything still works with no shifting or foam degradation after a year. What's not to like ??
Ya just gotta find an upholstery place that does custom work and has lotsa foam choices.