Ok, I can't be 100% positive, but I watched the Palace Scenes and Barge Scenes on Super Slow and ZOOMed In at certain times as well on the Widescreen Version and could not find Bossk anywhere. There is a Creature that looks like him, but does not have his uniform on.
Dengar is all over the place though. There are some real good shots of him (without backpack) from all angles as well.
Add that to my search for a PruneFace in Endor and my wife was really confused why I was watching the movie in Slowmotion, standing or at times kneeling in front of the TV....