Presumably one could install 12v. fans to increase fresh air flow in the space between the engine and the compartment ceiling, but if I recall correctly it has questionable affect for those who've tried it. I suppose that would depend on the number and size of the fans, and how they were configured. I imagine that they would be most effective after parking for the day, when ambient residual engine heat would rise up and soak the ceiling; a fan system drawing cooler outside air in would mitigate that soaking effect. I think also if one runs some hot water it helps dissipate engine heat a smidge through the hydronic engine exchange loop.
In our case, also an '06 Monty, we're graveyarders. By the time we're ready to crash at 3 a.m., open wardrobe door and open windows and/or AC fans have settled the bedroom thermometer a bit, plus the wife likes it warmer than me anyway. Otherwise for us, though occasionally annoying, the residual road heat hasn't been enough to prompt any efforts to structurally compromise it. Still, Robert, I'm curious to know how your shop addresses the issue.
Joel