https://www.techpowerup.com/267649/intel-core-i9-10900k-der8auer-de-lidding-reveals-accurate-die-size-measurements
 
Professional overclocker and extreme cooling products developer der8auer de-lidded a Core i9-10900K 10-core processor to study the processor's behavior with various kinds of custom cooling setups. It was discovered that the 10-core "Comet Lake" die measures 206.1 mm² in die-area. It is 9.2 mm wide like its predecessors, "Coffee Lake" 8-core, 6-core, and 4-core, but is 22.4 mm long, with the outer edges of its packaging material barely within a couple of millimeters of the adhesion point of the integrated heatspreader (IHS). Given what we know about how much each pair of cores adds to these dies, we predict that Intel cannot elongate this die to 12 cores, without having to remove the iGPU. der8auer discovered that using liquid metal TIMs and running the processor de-lidded shaves up to 7 °C off temperatures. Find more technical commentary in the der8auer video presentation.
 
Very interesting that this processor is very long in size but I suppose it had to be with 10 cores. 
 

So are any of the "F' parts actually missing the IGP portion, or are they all still deactivated IGPs? The graphics is still a large slice of that die, and why AMD can afford to be so competitive on its pricing since it isn't wasting so much die space for stuff nobody buying an 10900 will ever use. 

Good video presentation
 
I used a $2.00 utility knife to delid my 8700K that had conventional TIM (Dow Corning junk)..Worked like a charm.
 
For sure you'd need a delidding tool for a CPU with STIM..I'd try just using a liquid metal TIM between the IHS and CPU cooler if the CPU uses STIM and see how it rolls..Not any great big huge difference between Intel's STIM and Conductonaut..I would think that using a conventional TIM on top of a soldered IHS would just be blocking the heat dissipation/cooler absorption potential.