I had the adjustable backrest on the '07 Ultra that I traded in on the Tri
Glide. I thought I'd try to adapt it to the Tri and it turned out to be very easy. Since the backrest mounting bracket mounts to the passenger grab rail all I had to do was bolt it on. I couldn't use the front bolt so I used fender washers on the bracket to keep the bracket from flexing. I didn't try to mount the adjuster since I rarely used it any way. I used a pair of pliers to actuate the adjuster and I'll just leave the backrest in that position.

 

Had the HD Touring Adjustable Back Rest installed on my TG. Had to make a small mod and raise the mount a bit but works great!