That's funny lol, I think you might have graduated!
I'm impressed that you're able to do 9 drops, that is fantastic, I've never got beyond 5.
I'm pretty sure that the difference between the Christopher and Schulze formula is that Dr. Christopher has 1/8 part cayenne and Dr. Schuzle has 1 full part cayenne.
If you've got a bottle of the Christopher Eyebright and you feel you could stand it hotter and if you've got a bottle of the Cayenne tincture you could always add a half drop (that's drop, not dropperful lol) of the Cayenne tincture to the Eyebright and see how that is and if you want it hotter then you could add more of the Cayenne tincture. That would all depend on how much of the Eyebright is left in the bottle, if you don't have much left then adding even a half drop would be HOT HOT HOT lol! That is what I would do if I felt I needed it to be hotter, but you need to be careful if you choose to do that because once it's too hot there is no going back lol!