Anybody found something good to keep top-heavy stuff like flashlight mounts from tipping on rough roads, while leaving them loose enough for minor on-the-go adjustments? Last 3 flashlight mounts I've tried just couldn't tighten up enough even with all their spacers to keep it from being a constant struggle to keep the light pointed ahead instead of up or down when I'm bombing down the chipseal on the big hill at the work end of my commute.

I've thought about some sort of glue, but I still want to be able to tweak the vertical position for a given situation. Maybe some epoxy applied to the bars in lumps or strips and allowed to cure before reattaching the mount to make a rougher surface for it to grip?