Were you asking me?
If so:
It's good so far. The flashlight body piece (from a fake mini-maglite received as a stocking stuffer some years ago) is actually pretty strong over that short distance. It'd take a lot more force than the ziptie could dish out to do anything to it. The ziptie is definitely the weak link---over the 1.5cms it has a fair amount of room to stretch. If I take another half cm off the spacer the ziptie will probably be a little happier and also I'll have more clearance to take off my wheel.

If none of this works over the long haul, I'll consider drilling and tapping the chainstay bridge.