Looking at 21-24 foot Travel Trailers. This is the smallest ones that still have decent size bathroom and both dinette and sofa slide. Models include Jayco 24T, 242, and Heartland North Trail 21FBS. One unit has the optional 15k AC unit while others have standard...and less expensive 13.5. Question...would the larger AC unit be necessary to keep in nice and cool on 90-95 degree day...or is that overkill for such a small RV? I have no experience with RV's so don't have any idea ho long it takes to cool the RV down when you set up. It cost aro8und $225 more for the 15k AC. Also.....would the 15k unit be larger....and heavier?