Do I need to drill a hole through the bottom of my forks or is it okay to just safety wire the pinch bolts?
drill the axle near the hex area, then get some pre-drilled pinch bolts and wire in a series. I would not drill the fork leg. I race, ride the same 636. Ski
I asked about safety wiring a while back and the snippet from the rulebook that was posted in that thread said "axle nut and/or pinch bolts". If the pinch bolts are wired it seems there would be no need to wire the axle.
I race up here in Canada with the CSBK (National series) and with CCS/ASRA and Moto America and none of them have ever asked me to install safety wire to the from axel. Once you go through tech, just make sure you have an option to safety it, if they ask but I seriously doubted they will ask, since the fork acts like the safety of the axel. BUT if you're really unsure, then just put a smidge of GOOP (automotive silicon) between the axel and fork.