I have thought about setting up a totally different bank account for paypal....b/c if a buyer disputes an item, then paypal can literally freeze your entire account.
And don't get me wrong, I have 100% feedback on eBay (160) and 100% feedback on TB (46) but some buyers out there are nuts....and with eBay's new policies, it makes it tough for sellers...especially if the buyer just decides 'he doesn't want it'.....so if you have another account...you can transfer your money out and if they freeze it, they freeze none of your $$....might not be the right thing to do, but I consider myself an honest seller, and if my description is incorrect, I will stand by and make things right....but if things are just being made up, that is another story.
I have refunded $75 on a $225 bass before, b/c I didn't accurately explain the action....and had no problem doing it b/c I knew I hadn't done a good enough job in the description.
But if you honestly feel you did the best you could and explained EVERYTHING, I would tell him to ship the bass back and sell it again. Also, make sure the rogue buyer didn't add any 'scratches' conveniently to your guitar.