Be warned, for whatever reason, every single time I have used Fed-Ex with ebay, somehow they boxes get overstated and the weight does as well. I sold an AMP and other items, and was overcharged quite a bit.
eBay Seller Gets Surprise Bill for FedEx Shipping (ecommercebytes.com)
If you use ebay to ship fedex, don't just drop it off at a fedex store or hub, have them measure it and weigh it in front of you. Something does not gel. When my amp box, which has its size clearly stated on the outside of the box, gets overestimated by 2-4 inches in length and width, it is definitely fishy. Not to mention my amp apparently got fat and gained weight when I shipped it out too lol.
Bottom line, go to a fedex and kinkos, have them weigh it in front of you, take a picture and have them write down the measurements on the receipt. This way you will have something to dispute when you review your Fedex charges on ebay and it doesn't add up.
I no longer ship FedEx with Ebay, but I do have my personal FedEx account if I need to.