From experience - if you decide to ship it talk to the folks on the vintage board as they (we) have a lot of experience with shipping machines. For me, I'd never trust the UPS Store to do a good job unless they are very familiar with how to do it.
And if you leave it in the case, pack fabric or batting or whatever all around it so it can't shift at all. You should be able to turn the case upside down and have the machine stay put. At least a FW is rather light. You should see what a 35lb machine can do to a packing box when it's able to shift around inside.