Sure, it’ll get drier and it won’t move. Thermal adhesives have very poor thermal conductivity: I have an akasa one with around <span class=”a-list-item”>0.9 W/m·K. Epoxies like Arctic Silver/Alumina adhesives are better, but enough I think. And they are a pain to remove.</span>
I did consider soldering the copper shim to the aluminium plate, or at least the sides, but given that the components are so cramped together, shorting seemed more likely than a free floating (and conductive!) copper shim.