A tiny drop of heat sink compound and a bit of clear RTV on the corners will locate the heat sinks down.
WARNING: Be exceedingly cautious with RTV silicon in any electronic application! Conventional materials use Acetic Acid as the catalyst/curing agent, and releases a good deal of it during the process. Acetic Acid attacks copper and many other metals.
Use an ELECTRONIC (Neutral Cure) RTV.
https://www.alliedelec.com/gc-electr...EaAicDEALw_wcB
Peter Wieck
Melrose Park, PA