Mark,
There are two different events here.
First off the bars were 'materially misrepresented', meaning they were listed and sold for a certain saw and didnt fit. If Im understanding this situation correctly these bars were sold as 'will fit such and such bar mount Mcculloch', and that these were the sellers words. If this is true you could have stopped right there, filed a claim with paypal for the misrepresented items, won the dispute and kept the bars w/o paying for them. If the seller would have tried to demand that the bars be returned, they would have had to pay the freight because the bars were misrepresented in the first place... If the seller would not have sent the call tag or increased your refund then you keep the item or dispose of same as you see fit. Reason: Sellers are supposed to know what they are selling.
The second event centers around your decision to return these bars which really was done out of the goodness of your heart and on your dime. So, only because the seller requested that you return their bars, did you do so.
If you want to know what the sellers name and phone number are, log on to ebay and under the advanced search, request this sellers 'contact information'. Its on the left margin of the advanced search. You will need to enter the item number and some other info on the ebay form and they will send you this sellers full name, address and phone number.
In addition, since you used USPS, make a report to the Postal Inspector in charge of your Post Office and they will get the parties concerned out there looking around for these bars which should be easy to find. Believe it that they will ask the carrier if he or she left an empty or torn package. If the carrier says no, then they will surely look at this seller a little deeper with suspicion.
I would dispute the transaction with paypal and state that the item was materially misrepresented as long as this is correct. After ten days, I would then escalate this 'dispute' to a 'claim' under the paypal rules for buyers. Paypal will not automatically escalate the dispute to a claim, you must do this. This seller has $200 worth of 'buyer protection' afforded to you as the buyer in this case. If you are successful in your claim your total payment to the seller will be refunded, it has nothing to do with whether the seller has any money in their paypal account.
The fact that you returned the bars is secondary and was your good faith attempt to make the seller whole.
If you have questions, pm me.
Best wishes,
Bob