I use a graphite/ resin mix or JB weld.
I give a description about it Here
You can see more lights with this if you view my sig picture.
It can compress many times but is weak torsionally so making a sandwich with thin copper sheet is a good idea. Other lights i have used it in i make the pill at the negative end of the battery so there is no twisting on the QTC material.
The tritium vial is epoxied inside a plastic tube. The vial goes through the end of the keyring attachment but the plastic tube butts up against the underside. The hole closer to the light body is larger so the plastic covering slides through it onto the button.