Its a mustang seat and I love it. Was hanging on the wall in the parts department of the HD dealer.

 

With my 518's at full lock on the steering it just clears the tank and stock cap / fuel gauge with the angle I have mine mounted at. 550's (if lower like a drag bar) might clear with the flush caps but you might also have to roll the bars up if the rise is less. I wanted my bars tilted down for a comfortable grip angle (and it looks cool) so the slightly higher rise allowed that comfort for me and cap clearance. Seems like a simple upgrade to a bike but there are so many variables.

 

That's what I was thinking, thank you for the confirmation.