So in October you're gonna SEND IT with me for long distance and find out? 4500-5000 rpm for a couple of miles WOT!
but.... I agree with the others don't mess with it till you're ready to tear it down. Maybe buy the carb (and other stuff) for the last run and see what/if anything changes. I wouldn't think going down to a 750 will help your top end, you'll need more CFM and flow thru the heads to get a big change.
When MPD did my pump I gained 800rpm with no other changes.
I may try the Demon 850 again, the 750 runs awesome and saves fuel but still we always want more. The biggest issue for me is tuning the carb for idle and max rpm. I just can't figure it out, even though it's simple changes. In reality I need heads and a cam to make the little extra power we're looking for. My setup is tapping out at 5500 - 65mph, but as you know it's always FULL SEND!