I only make HP soap (patience issues...) and have used Cinnamon for color and Cinnamon Bark eo for scent. You have to be VERY, VERY LIGHT handed with the cinnamon, because it is very strong and a serious irritant. Generally, you can use half the amount of FO or EO you would use in CP, which comes out to about 1/2 oz ppo--not with cinnamon. A few drops--about 5-6 ppo--of Cinnamon Bark EO is safe. With Cinnamon Leaf EO, I hear you have to use even less because it's such a strong irritant. I also add it right before molding and haven't had any issues with discoloration or texture change. It's not a very strong scent, but you can tell its there; if you need a very pronounced cinnamon, a FO might be your best bet.