Replying to Mounting Alpha 1's?

Ok so I'm pretty sure that I am going to put some salomon sth 14's on my alpha's as it seems to be a very popular binding which is light and strong, unless anybody comes up with anything uber good. So on my alpha's there is a center mark, then -2.5 which is factory recommended and then -5 which i have no idea why they put that on there. I was thinking mount at -1.5 or -2, what a peoples thoughts and has anybody email tyler about it? Any help would be good, thanks!