I recently bought the j ski whipit which is 90mm waist. I did a bunch of research on binding size and most people on ns say that you wanna get the same, if not smaller brake width as its quite easy to fit em on. So I bought 90mm marker griffins. Then i took the skis and bindings to the shop to get it mounted and it didnt fit, the brake clipped the edge of the ski. I looked like a right fool. What I do?
Your brakes would fit just fine if you mount something like 15 cm in front of centre. Your skis are 90 in the waist not where the brakes are, chances are they are a mm or two off on each side. Just bend the feet out by hand enough so they don't clip the edge of your ski.
I have 90mm marker griffins and my skis are 92mm underfoot, just carefully bend the brake so it fit and you should be all right. People recommends to buy the same size because if your brakes are too wide, they can bend and break.