I put a third 12.5 K air conditioner on my 2006 Winnebago Voyage in place of the Fantastic Vent in the Kitchen area....no extra support needed or used. Best thing we ever did! I can run all 3 compressors (total of 36.5 K)on my Onan 5500 generator or 50 amp service. I have pictures and a write up on RVForum.net in the Winnebago forum.
I also had the Ultrapower, and was grateful to recieve a full refund on it as there was never any power increase, and in fact the MPG DECREASED. :E
I too am interested in hearing about the 5-Star tuner. :)