We are upgrading (from our 34' 5er/ Chevy 2500HD Duramax combo) to a 2017 XLR 422AMP at a whopping 45' (I think it's XLR's biggest!) and a tad over 20K loaded = new TV!
Now that the brand new Duramax has 20% more torque in 2017, also making it the new 'King of diesel pickups' in both HP and TQ, my choice was clear...
3500HD Dually/Duramax, High-Country Pkg (same as the Denali Pkg in GMC, just not that fugly front Denali chrome grill!), all fully loaded w sunroof... OTD priced at $70K. cough-cough
... On this note, I could not order in a short box, (in DRW) it has to be a long box. Being a Crew Cab also, this will be a long mother! Another note to this (lol), the long box gets the 5th wheel hitch (pin point) more forward (over the rear axle), the short boxes will have more sway naturally because they have the pin point further to the rear. So bad on the box length (for me), but some good comes of it as in the towing factor mentioned!
I know my current 2500HD SRW could handle it (most of the time), just that those Semi's and cross winds would be the real buzz kill. PLUS!, throw in the fact that your insurance Co. won't pay on a possible accident if your TV is underrated for what you're towing? Yep, insurance companies look into this and it's a legit (legal) reason for them not to pay you on an RV (in tow) related accident. So, cover yourself!
On the bigger is better statement above^^^^, I have also ordered-in the over-spec'd 25K lbs "drop in" puck hitch as well. My current 20K 5er hitch will be sold hopefully along with my 2500 SWD truck this spring.
TV's and weights thereof are a very important part of our RVing experience. Happy and safe travels everyone.