ORIGINAL: Paternguy
Do not run the engine with out the washer, the nut will burn its way through the prop and the engine will then trow it.
Take your original nut to a local machine shop or use a grinder if you have one, and machine it down to half its original thickness.
One of the other folks is grinding down the flange of the adapter so it fits inside the nut (where the locking nut would normally fit itself into). Crappy weather here for last 10 days so I haven't had a chance to try this arrangement out yet.