I owned an Alfa Gold 38.5 ft 5th wheel with the basement air system. I crawled around under that trailer for a while sealing up every single connection to stop the air leaks causing the system to not cool like it should. The a/c unit put out cold air but the trailer always seems to be luke warm. After I got those leaks sealed, the trailer became cold, and I mean really cold when we set the thermostat low. I ended up helping another couple that had the same trailer only shorter fix their air leaks to improve their air cond system. Before adding a second a/c unit you may want to investigate the leaks in your system if the a/c unit is producing cold air. It will make a difference in how well it will cool.