When are you going?
We did this trip this summer. We took the I95 to the 101 over to Manchester. Then take I93 north to the 202 to the 9. Take the 9 into Brattleboro, and then turn north on the 5 for three miles to the Brattleboro KOA. That would be your halfway campground that can fit your rig. Beautiful drive, the hills are not difficult and the roads were great. Next to the KOA is a pick it yourself farm. We availed ourselves of the opportunity for hand made peach pie and sweet cream ice cream. There's a Shell on your right, just as you're coming into Brattleboro that has a diesel pump behind it that's an easy in and out for your size rig.
From there, go back to the 9 to the 7. Get on the I90 for just a few miles to the I88, then take the 10 to Cooperstown.
If you want to stay on the interstate, you can go from I95 to I290 to the I90 and then catch I88 to the 10 to Cooperstown. If you go that way, Springfield MA has a KOA that will also fit your size rig. If you're into it, Springfield is where Six Flags New England is located.
2021 Holiday Rambler Armada 44LE
2021 Jeep Wrangler High Altitude toad w/Ready Brute Elite II