Hi Ivy, thank you for your kind words but I don't think that does prove that Felis 2 is dominant to Gingersnap - though I suspect it is from my tests so far - I just don't have the proof. Yet.
To go back to your proof and look at it line by line -
Oliveria Felis 2 (Passion Teacup) is bred with Denver - a Maltese Black Chinchilla
they make a Felis 2 kitten (Jael), now Jael shows Felis 2 but we don't know his hidden fur, except that it isn't Maltese Black Chinchilla (as that is dominant to Felis 2)
Jael is then bred with Ogelsby - a Ginger Snap and they make a Ginger Snap kitten (Cynric)
Cynric is then bred with Yalissa - a Midnight (second most recessive fur on the grid) and they make a Euro - Grey & White kitten. As you said, the Euro - Grey & White can't be Yalissa's hidden fur, so it must be Cynric's.
And therefore it must also be Denver's hidden fur - as it can't have come from anywhere else. So, Jael must be Felis 2 hiding Euro - Grey & White.
This is probably the main reason I prefer to test starter cats that hide the unplaced traits - it's much cleaner.
This is where I'm up to on my testing. I've both this starter and another working with Ginger Snap mates but the other two kittens produced so far have both been Genesis. I bought Hunter Baby (the Ginger Snap) so can't be sure of his purity - though he's solid Ginger Snap back to his great grand parents, so until I pull Naill's hidden fur I can't be sure if we have Felis 2 placed or not.