The combination of the bolt very close to the card and the spring on the far end of the clamp would be about perfect if the spring had a high enough tension. After all, you aren't wanting enough pressure on the RAM to crack it
Curious though, what's your beef with using an Arctic Alumina mix? Holds well and can be removed if done with the epoxy based version used only on a small section of each end and the non-epoxy version used in the middle.