You just have to play around with it and ride to find out.

 

13" on my Iron makes it lean over way more than stock. When I park in any type of grade I always put the stand going uphill.
When checking the oil I just slide something under the stand to bring it back up to normal.

 

This is what I went with and love them. Almost 1000 miles on this setup and some 1" lowering blocks and all is well.

I have an extra set of 13'ers if anyone is interested in them for what I paid for em. PM me

 

Set preload so that you get about 1" sag when you jump on.

 

Dan, you touched on the very thing I am going to post. I have a 2007 1200C that came with 11.75" shocks that transferred 95% of every bump to the chassis. I installed 13.5" Progressive 440 standards. I weigh 205, I set the sag at one inch. With me sitting on the bike the center to center bolt spacing on the shock mounts is 12.5". This seems to be perfect. I do have the leaning too far issue but carry a 3/4" wood block and toss it under the side stand when I have a concern. It is my opinion that guys with 13" or 13.5" who don't have the leaning problem have too much sag and not enough pre-load.

Supposedly there is a side stand available for the R model that eliminates the excess leaning issue as the R had 13.5" shock as stock.