My 2004 Allegro Bus had a Xantrex Freedom 458 inverter, which I replaced with a Xantrex RS2000 true sine wave inverter. It went into the same location, which was a basement compartment near the rear of the coach. There was an air intake scoop on the bottom of the compartment to bring air into the inverter's fan. I too had issues in hot temps where the inverter would overheat and shut down until I cooled it off by opening the compartment door. The problem was not that I wasn't getting any cool air into the compartment. It was that I wan't getting the hot air out.
There was a louvered vent at the rear of the compartment that supposedly allowed the hot air to escape into the rear cap by the engine. I removed this louver and mounted two 120mm computer fans behind the louver. Then I wired these two 12 volt fans to a thermostat in the compartment. Whenever it got hot, the fans would kick in and cool the compartment down. That was the end of my problems. You may want to see about doing a similar mod to your system. Apparently Tiffin realized this situation because they now locate the inverters in the main basement storage area where there's lots of air.
Mark & Leann Quasius
2016 Cornerstone 45A
2007 Allegro Bus 42QRP (Sold)
2012 Jeep Wrangler Unlimited - Rubicon