It looks like steamboat's heat sink is working nicely:
The board is now mounted with thermal compound on a beautiful black heat sink sent to me for testing by steamboat. The chips are barely warm now.
Note though that BKK still has the clock rate about 1/2 of what it will be (pending a capacitor that needs to be changed), so the chips will most likely end up being hotter than "barely warm." But still -- great news.