OK - if all you are doing is hitting an occasional curb, why do you NEED a 14mm axle? Just get a new 3/8 wheel. If you NEED a 14mm axle, then you're probably planning on riding in a manner that an AL Race frame isn't best for.
If you INSIST on filing your drops, you need to remove an equal amt from the bottom & the top of the dropout to make it 14mm. Otherwise you'll subtly change the geometry/handling of your bike. Slotted 14mm is a better option.
-Bill