Downsizing, sort of?

good afternoon everyone! hope you are doing well. First I guess a little bit of information on my current situation? if you want to call it that. Anyway right now my and wife and I own a 2015 RAM 3500 limited dually long box. Love the truck, it has severed us very well. Last year at the lake I was sitting in the lawn chair looking at it and just began to start to really contemplate the justification for it. While we do need a dually to haul our fifth wheel/boat combo to the lake I have been finding it increasingly more difficult to justify the 850$ a month. In reality it only gets used to its actual potential for 4 or 5 trips a year, equaling MAYBE 1000KM a year of pulling our rig to the lake. The rest of the year, while a gorgeous, comfortable truck hauls my to work, and is generally the goto vehicle for the 1200KM trip to the in-laws. But after owning it for almost 4 years its only got 68,000KM on it. Ontop of that we are building a new home at the local lake this summer so in doing that we will cut down our camping almost in half yet again with just having our annual 4 week holiday at our favorite lake.
SO I don't know if any of you have done this before... maybe I am crazy. But we have 4 years left on the loan of the 2015. I am debating on taking the equity we have in the 2015.... and looking at getting into a really clean 2007 to 2009 ram 3500 mega cab dually Laramie pkg with heated seats/steering wheel and driving a truck without a payment for a while. Any opinions on this? I have a 2007 ram 3500 SLT dually welding truck with the 5.9 which I do like, the interior of course dosent touch my 2015 but one cant expect it too.
what I am struggling with is finding weight towing capacities..... the specs of our fifth wheel is 14,270LBS loaded weight, with a pin weight of 2270LBS. Behind that we tow our 20 foot walleye boat weighing in at 3500LBS. All I have found thus far is charts saying a 2008-2009 mega cab dually is good for around 16,500LBS, but get difference answers from other sites. Ontop of that the previous owner of my 07 welding rig used to haul a 40 foot gooseneck with a 21,000GVWR that he regularily had maxed out.
I guess the question is can a mega cab dually with the 6.7 handle our rig which is 14,270 fifth wheel with 3500lb boat? my gut tells me yes it will. Plan is to go with the reese goosebox pinbox for the camper so as to have nothing but gooseneck couplers in my fleet. from what I can tell our montana high country has a nose cap that is made for short box trucks.


Any opinions would be greatly appreciated.