I have a 1991 MB-3, and I think my frame is very similar to your 1993 XO-5. I don't think you can mount sidepull brakes on an XO-5, because the distance from the fork crown and seatstay bridge to the rims is too great and the seatstay bridge is not drilled for a brake. As to your specific question, the hole in the fork crown is not drilled for a recessed brake, and you can tell because the hole is not enlarged in the rear.