Some of the better Fila breeders actually find that two 'perfect' examples don't give the best pups. Often, at least with Filas, you get a much better litter of pups if you take two dogs who may have some extreme characteristics on opposite ends of the scale to achieve balanced pups. You may get one or two that have more of one parent's characteristics than the other, but that isn't necessarily a bad thing, as different owners are often looking for an emphasis on a particular breed characteristic.
I would think, if Roxy Mae's snoot is a little long, you can look at sires who might have snouts that are a little on the short side, assuming there aren't any health issues that follow the shorter snouted Chihuahuas.
I think you've got a good plan mapped out, Pro, and working right there with a vet certainly is a plus! Grammy (Bubbatd) and Pits are great resources, too. Both have so much experience with breeding ethically and successfully. I know I'm going to be depending on them a great deal with it's time for Shiva and Kharma to have a litter - although I'm dreading it! Charley's choice. If it were my call, I would consider a litter out of Kharma, but not Shiva, as Kharma is a classic working Fila and is a beautiful example of a Fila from, among others, the Jaguara line. I love Shiva, and she's a beautiful creature, but the show line on her father's side has diluted her temperament and her body type isn't as correct as Kharma's. But Charley prefers Shiva.