I have the Progressive 430 HD 12.6" on my FXDF. They are .6 longer than stock, but didn't raise the back in a noticeable way. Keep in mind the spring rates for Progressive shocks vary depending on length . Looking at their doc (link below) I found that the 12.6" HD had a spring rate in between the Regular 12" and HD 12" that were listed for my bike. I have the non-HD springs in the front and have been very happy with the ride and performance.

http://www.progressivesuspension.com/pdfs/7100-105.pdf