Problems with Shipping

[ruralbess3]

I sold an item with a shipping weight of 16 lbs, box measuring 19"L x 18"W x 17" Tall, shipping from Illinois to California.  Ebay shipping rate Parcel Select $69.44, Priority $67.65, and FedEx Ground Home Delivery $36.98.  Thinking there is something definitely wrong here - too much difference in FedEx and USPS - I went to the FedEx website and calculated shipping and for these dimensions, it was $75.64.  The reason being, that Ebay is not calculating Dimensional weight shipping on the FedEx label.  According to the FedEx website, I have to pay shipping on 42 lbs because of the size of the box.  I don't know whether to send it with the 16 lb rate, send it at the 42 lbs rate, or just what to do.  Question - Has anyone else ran into this problem?  I don't know how much to refund the Buyer on the difference between FedEx and Parcel Select that he paid, because I believe the FedEx shipping label is wrong at $36.98, and I don't want to be stuck with the shipping.  Of course calling Ebay to get an answer does no good.