You weren't satisfied with your Twofish but I've used a couple of them extensively and they work for me. One's on the helmet with a AA light and the other I've used on the handlebars with an 18650 P7 flashlight. Then there's another we've used for a tail light on another bike with a red LED 501B flashlight. All hold the flashlights reliably; they stay in place and hold up well.

The heaviest light of those three weighs about 6 ounces. I'm sure there's a limit on how heavy a light these holders will keep in place but a single 18650 light seems to be well within their limits.

I balance the flashlight on the Twofish and cinch the Velcro tight. They all go on and off quickly and stay in place. In fact, while they stay in place, some other lights I've used, such as the MJ 808, are prone to rolling forwards and down on the same handlebar. With some of those other lights I've added a strip of inner tube as a shim to reduce slipping. But I haven't needed that with the Twofish; they hold just fine.

Perhaps there are surfaces that the Twofish doesn't grip as well. I have run of the mill, round, aluminum Cannondale handlebars.