I've noticed my cap sets really tightly in the artemis but doesn't do this with the mini stem (same tip and cap on both). I normally heat 3 seconds past the click with the mini stem but defo needs a bit more with the artemis, will give 5-10 seconds a try.
Mines is the same, it takes the same size of o rings but I had to install new ones on my tip in order for it too fit tighter. I would also recomend not using a lubricant on your o rings when using the artemis aswell that seems to stop it spinning for me. It was a bit annoying at first but...
How are folk finding the T.H.C cap for the hyperdyn? Is it a worthy upgrade? Kinda dissapointed in the stock hyperdyn to be honest. Willing to give it another shot if the T.H.C cap improves performance.