Here I am obsessing about putting thermal compound on the outside of package, when duh, of course the leads are going to be the lowest resistance path for heat out of there.
That leaves the question of where the heat goes once it's in the ground plane. Maybe most of it gets conducted to the enclosure, and out the shielding of your antenna cable, via the BNC?
I've got some silicone thermal pad, thick enough to fill the gap between the bottom of the PCB and the enclosure, I wonder how effective that would be at pulling heat out to the enclosure too.
