I know -9 is the reccommended mount for 191 Billy Goat, I think it may be closer to center. That said, the guys at ON3P designed the reccommended mounting points to work perfectly with the reverse elliptical sidecut in the nose of the ski (which starts at boot center I believe). Any further forward and you risk messing up the way they ski by interfering with how your weight distribution interacts with the REC in the nose and the regular sidecut in the tail. I would say just mount them with the boot center right where that mark on the sidewall is and you should be good to go. If you're really worried about it, that's why you have schizos so you'll be able to mess around with the mount. If you're looking for a more bidirectional ski/something with more tail, I don't know why you're getting the Billy Goat, and you should take a look at the Caylor or the Jeffrey (assuming you're adamant on getting a pair of ON3P's).
Also, about the bindings. Unless you're really concerned about the mounting point, I wouldn't necessarily reccommend griffon schizos. If you've already been using them and have had good luck with them, sure keep them. If they're new and these are the first skis you're throwing them on, I'd look for something else. I've heard lots of stories of the bindings sliding forwards/backwards in the track while you ski on them. I also personally prefer something with more metal in it, and griffons are known for being kind of plasticky. Anyway, that's just me, if you like them already, then by all means keep skiing them.
I hope this helps, and I hope you're stoked to be on a brand new pair of Billy Goats because those skis are fucking sick and I'm sure you'll enjoy them. I can personally attest to ON3P's exceptional build quality; I've been skiing a pair of 191 Caylors for the past season and they've held up better than any other brand I've tried. They make bomber fucking skis, that's for sure.
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