From the contact paper test, thermals could have been greatly improved simply by telling CoolerMaster to fix their existing HSF design.thermals could have been improved with a $30 HSF.
If the copper slug surface was simply slightly convex instead of concave, it would both fix the poor center area contact issue and increase contact pressure without changing anything else. Total cost: a few minutes of CAD time to re-program the CNC lathe that turns those slugs and maybe a few more minutes to CAD a replacement press tool to make sure it doesn't cave the slug face in during press-fitting if the original press tool isn't already designed that way..