I have pulled three different GNs extensively with two different F250s with absolutely no issues. Had a 2001 F250 that pulled a 2001 Merhow 2H GN and a 2005 3H GN 4-Star. Now have a 2012 F250 and pull a 2013 Lakota 3H GN with small LQ. Since Ford took a leaf spring out for a cushier ride, we installed air bags so we could level the ride, but despite the 20" rims, it is not too tall. Completely stock other than the air bags. Wish I could post a pic of my rig to show how it is properly leveled.
Yes, that was my original intent -- to ask about the actual bed being too high. I see now that my gooseneck can be adjusted, but seems like I still want the unloaded trailer to be relatively level, not tipped up too much.
I had not even thought about the other issue, that of the bed sidewalls being high. So even once I get the trailer at the right height, am I going to have to worry about the bed sidewalls? A related, but separate, issue!
I have gotten really good info here, thank you everyone! And of course I welcome further comments!
Had this same problem with my F350 and Kieferbuilt GN 3H. Ended up taking the trailer to a welding company that essentially raised the trailer off it's frame a few inches and rewelded it. IIRC it wasn't super expensive.