so here’s what i did- I drilled into the throttle cable housing and secured it there.
I used a selftapping screw to drill through the vista cruise and the housing to ensure a good fit. I had to do this while the pieces were off the bike due to limited clearance between the throttle tube and where i wanted to drill. the first hole brought the VC off center and caused it to bind when disengaged. so I had to mount the throttle housing and the VC, mark a new hole and redrill it. getting the hole on the protruding ring of the housing made sure the VC would sit flush and not at an angle
then I screwed the housing and VC together while they were off the bike and marked the inside edge of the screw, removed the screw, and hacksawed the end of the screw off so it sat perfectly flush inside the throttle housing. I sawed off the tab on the VC to avoid interference with my heated grip cable.
this is the throttle cable housing, the VC, and the washer installed
I had to trim a bit of the rubber off of my grip flange so it releases properly.
I imagine this thing will be suuuper handy on longer trips.
tiny nitpicks and things I might do differently next time:
1. I would use a flat topped screw, countersunk into the VC to make it perfectly flush when I install this thing on my next bike
2. if I had room on the bar end I would shift my grip outwards to avoid having to trim the rubber flange