As I pointed out in the other thread, you can swap the axle for $6. If the new fork's dropouts are designed to be a tight fit on a 9mm axle, they may be 9.2-9.3mm or so. A 3/8" axle simply won't fit without some metal removal. Assuming the fork os half decent, my opinion is that fixing the real issue (the wheel's axle) is the cleaner option than filing the dropouts.