about a bad buyer Bigboy68

Simple solution.

If you want to sell parts and someone offers up the payment plan, if they don't send a non refundable deposit and a DEFINITIVE drop dead date... DO NOT DO THE DEAL!!! PERIOD!
No BS excuses later on. I've had some very popular members ask me to hold parts and then saw them buy a part, listed after my stuff was posted and our deal struck, that I was also interested in within a few days... Yeah that's a deal breaker...

I usually go with "If I still have the part when you have the $ to complete the transaction in one go, great. If not, hope you find the part elsewhere." Not going to be a storage facility for someone so they can list the item elsewhere and turn me into a drop shipper. Yes, I got that one once too...

Cash and carry, this ain't the layaway store.

The bad side is you may have interested parties that go elsewhere because you decided to go with the payment plan. Sucks, but, post it up again move on. Store that in the noggin and don't do the same thing again.