I am about to make a similar switch, but likely to the Phantom 7. I wanted the 7.5, but I am a lefty, so only have the option for the 7. I'll let you know once its ordered and I can play a few rounds with it.

Wanted to update here. I actually went with the 5.5 because I just couldn't get over the double bend of the 7 (again I'm a lefty, so options are limited). Should be here in about 3 weeks.

When I tested the 5.5 at the store, I didn't want to like it, but because of my stroke the fitter recommended it, and I was draining putt after putt.

Have you ever considered getting fit for a putter? I didn't really believe in it at first, but after doing my research, it does matter and makes a difference