Here are pics that Phil at Yaffe sent me when I was considering the 21" w 7* trees. It's a very subtle change. But Phil said with the trees and a 21", you wouldn't need to lower the front. Which to me, was a plus.
The diff in the last 2 pics is 21 vs 18 and about 2" kicked out.
You could run the 21" as well. It will stretch the front out 2", I believe. Then when you want, you could run a 23". 808Bagger has a ton of info on diff methods. Before I decided to cut the neck, I was gonna just run the HHIs w a 21".....but like you said, this site will cost you money. Haha.
I purchased these HHI trees to swap out with my trike trees to get another 1" higher on the front end. I've decided for time reasons (Sturgis) and financial reasons (Sturgis), I need to sell them. I opened the box and that's it. They are brand new. I'm asking $700 shipped to the 48 states.