Nice calculators.. It keeps you at your trucks GVWR if you pretty much know your other weights. Might help newbs see how fast stuff adds up and not just look at the trucks "tow rating" and think they are 'good to go'... ;)
In my case, it says I can't tow the trailer I'm towing.... A #5000 GVWR 22' TT with a 1997 F150 with a #6250 GVWR.. I know I'm over it's GVWR, but the trucks got 255,000 miles on it and I've been towing the same trailer since 2002 without imploding the world around me.. :)
What works for me is not going to necessarily work for others and that's fine.
The calculators is a good starting point and should at least make the user aware of where they stand on their individual weights and the user can decide what's right or wrong for them... :)
Mitch