I've heard of being able to sticker a jeep to us on OHRV trails but never an OHRV for the road.
I believe the class 6 road must be designated open to OHRV's/ATV's before you can ride on it and almost all snowmobile trails are off limits to ATV's, OHRV's, jeeps and trucks. As it should be because they do a number on the trails especially any wet area's.
And remember the instant you turn off that class 6 road you are trespassing on someones private property weather posted or not, and subject to fines.
Below is a link to areas open to riding, you can find more with a little searching. I do not think there are many if any worth trailering to south of the White Mountains. Most class 6 roads, if open are not very long and you would grow board with them very quickly.
http://www.nhstateparks.org/experien...FQZnOgod6CQAEg