I tow our 27.5 rlts with a 2001 2500 4x4 Ram. I run 285 tires on it and have it lifted just a little. The bed rails are right about 59 inches if I recall. Which I think is very close to yours at least the new ones are about that height and the 2012 are the same generation so suspect they are the same or very close. The trailer is running the stock 15 inch tires. It does not tow level. It is not much off but it is off. According to my tpms on the trailer tire temps are very close to each other so the amount it sits nose high is not transferring too much weight to the rear axle otherwise there would be a temp difference I would think. I have been contemplating adding a sub frame to it so that it will tow level. However I have not taken it in to see how much it will require. If my math is right it is going to be about 2 1/2- 3 inches. I could get close with some larger 16 inch tires but am afraid if I go that big that the space between the tires starts getting very small, 33 inch spacing, tires are 31.8 diameter so that only leaves 1.2 inches between the tires as well as the space above the tires starts getting very short and get concerned about the tire hitting the floor on large bumps. So sub frame may be my answer. I am also right at 6 inches on bed rail clearance. So a sub frame would allow me to increase that distance an inch. Local trailer repair shop quoted me off the cuff 700 for the sub frame. I am getting ready to buy a new truck within the next couple months so have been waiting to do the sub frame until then just to make sure.
It tows fine the way it is in fact no issues at all but would prefer level and just a bit more clearance at the bed rails