I went from a F350 pulling a 37 foot fifth wheel to a 36 foot diesel pusher without any problems other than it was too short. Did not take long despite what was posted on here to learn finding a site for a bigger rig was not a problem.
For FT I would suggest 40+ with a tag axle and then you will not have to worry about how it will handle as they will handle very well. Sitting higher up you can see better and I still do the 1500 miles to CO in two days. It's that easy to drive a big DP.
If a dealer will not let you test drive, let them know you'll find another dealer. If it' an insurance issue then sign a contract with a dollar down that you can cancel for any reason in the next three hours.
