I agree with everyone. I have a 2008 Monaco Diplomat 40SKQ with a 400 ISL and Allison transmission. I tow a Chev Suburban. Lowers MPG a bit, slower going up hills, faster coming down hills(need to brake a little more often) I use M & G air brakes, -- long story short -- one of the reasons I bought the Diesel pusher was because I had a Suburban and wanted to be able to tow the heavier vehicle. I am getting used to the idea of slowing at the top of steep grades - using my exhaust brake and down shifting - and an occasional braking to keep my speed down as I go down steep grades. I am coming to understand that it all depends on what you want and are able to tolerate. I am learning that more and more as I read comments on irv2.com
Good luck with your decisions.