I have the;

Seat back adjustable mount 52596-09A
Seat back to accompany mount 52591-09A (It is the seat back specifically for the RKC)
Hammock seat 52000003

I am 6', 235. I sit in a good position.
I can place my feet flat on the ground at a stop.
I have room to adjust the back rest forward or backward. And do so after some time in the saddle for a change.
The mount does fit as shown in a previous post.
The mount does not come up above the top of the seat. My wife and I rode it for a few hours last Saturday and the mount was not a problem. As I use her as my backrest when we are two up, I did not use the backrest. I had heard the same rumor about the mount being too high. But chanced it thinking I could return it if there was a problem. It is a good decision.

 

Matt I'm 6'2" 245lb. so that's good info, thanks.

Anyone using the Hammock seat part# 53051-09 with the HD adustable backrest?

 

I have tried both seats, with my adjustable rider back rest.

Seat 51000003, hammock for both rider and passenger, has a slightly different fabric design on the nose of the seat. It also seemed to sit me up and forward a bit compared to seat 53051-09. Seat 53051-09 was the first one i tried and it felt the most comfortable. It seemed to be a little shallower in the bucket portion, which I prefer. Also, after a bit of use, I have seen that seat 53051-09 wrinkles a bit at the bend in the nose, right where the different fabric design change is on seat 51000003. I suspect that was the reason for the different design on the nose.

Overall, the back rest was not an issue with either.

I like the look of seat 51000003 over seat 53051-09. JMO.

At the end of the day I did not buy either. Just not enough difference from my stock FLHT seat, which is different from a FLHTC or FLHTCU seat.

High milage days do not bother me in the stock seat.

Good luck and just my opinion.

 

Thanks for your response old v twin. The stock seat just ain't going to work for me but I want a seat that is compatible with the back rest.