Man, I need some more time to mod gear. I just got a FR-777, too. :)
Upcoming mod: replace all the sliders in my SH-101 with replacement versions. Should be ok, but since I'm gigging with it a bunch, I'd like to install proper dust shields of some type into it... I've been thinking about using chunks of plastic with a hole cut for the slider post, but who knows if they'll slide back and forth as well? Gotta experiment, I guess.
One wierd thing - the SH-101 uses the metal bottom cover as a common ground... without the cover in place, the synth just doesn't work! Took me long to figure that out - installed a big (10,000uF) capacitor in there to cut down on the noise, and when I went to test, I figured I'd broken something terribly... :)