Just curious...would a fantastic fan or Maxxfan set to exhaust in the bunk room help pull the air into there to make it more comfortable? I am not sure how that would work but figure someone on this sight would know.
Also, have you seen the tent in a vent mod? I saw it on this sight and we tried it. It takes longer to cool the trailer down initially because you force all the air through the vents instead of dumping it straight into the living area but the air in the vents comes out much stronger than it did before. Thus it forces more air into other areas of the trailer. It's an easy mod and has really helped us. Since you have a 2nd AC for the BR, you could close vents in the bedroom from the main AC and it will help to force even more air into the bunk room and living area.
One other thing, we were advised from a friend to tint our windows darker. We did and that has helped tremendously when weekend camping (TEXAS...It gets HOT!). The only downfall with the darker tint is it stays a little too gloomy inside the trailer for my liking. We are outside most of the day anyway. I really like natural light. We can still see out all the windows just fine, it's just quite a bit darker inside. It's a toss up...cool vs light...in Texas, cool wins (for us anyway).