tailgate height ?

When I bought my 2015 Denali my tailgate was the same. I took all kinds of measurements and was worried if I would have enough rail clearance was the hitch was installed. With the B&W hitch I have 3 height settings 17, 18 , 19 inches. When installed I had it set at 17 inches. Once I hooked the 5er up the truck settled a little. I had 5.75 inches of clearance on bed rails. I raised hitch to 18 inches and I still ride pretty level. I can leave the truck hooked on overnight stays and stay and not have to worry about being nose high.

Do have one issue though. I have a slider and when I put it in the rear position it will hit tail gate. So far I have not needed the slider.
I will make a tailgate support that I can open tail gate a little so it will clear in all directions. Although I may never need it. I can turn 90 degrees with out hitting cab.

I'm at 57" also, and it's not a problem for me.

That's about what mine is at and no problem the FW sits about 6" above the bed rails.

They will settle down to 54-55" or so.

Only a problem if you let it be a problem. :S

Mine is about the same height as yous, and we have about 5-1/2" clearance at the bed rails, and a tad nose high, I have a CorrectTrak system yet to install which will raise the 5er about 2' which should put me just about level.

It depends ... but likely workable, a lot depends on the build of the trailer and how high (or low!) the pinbox mount is.

My bed rails are at 57", clearance of the front of the trailer over the bed isn't an issue, but I've been towing a bit nose high. My Reese R16 hitch is in its lowest mounting position and my Sidewinder pinbox (pinned) is in its highest and I have, best I remember, right at 6" at the tailgate, more as you go forward due to nose high attitude.

Due to blow out in November and damage to one of the axles, I'm replacing axles and while at it, adding a 3" lift to the trailer and moving from 15" wheels to 16" which will raise the trailer by a total of 4 3/4". Axles are due in any day now, at which point I can confirm arch of springs and make final measurements to confirm I'm not going too high. Even at 4 3/4", I don't anticipate I'll be perfectly level, but close enough to where a measuring tape will be needed to confirm.

Depends on the 5er. My 2012 F-350 dually is 54". I looked at Dodge and GM in 2012 and they were much taller so I went Ford for that reason. I have a 39' 5er and even with the ford its a touch front high when towing.