can I use a different shipping method other than what the buyer selected?

[mikedropshop]

Hi - Im still relatively new to Ebay selling and am unsure how to proceed

-i advertised an item with 'buyer pays for shipping'

-a buyer accepted the offer and selected USPS ground advantage but the amount ebay shows I will receive for shipping is only 60% of what the actual label will cost!  

-i messaged the buyer to ask if its ok that I ship with UPS ground as that will be less expensive and within the amt is he paid

-the buyer has not responded for a couple days

-so now i dont want to delay shipping.  is it ok with ebay rules if I just  ship with a different shipping method since the buyer is unresponsive?

-also , in general , if I estimate the size/weight of the item and then it changes due to packaging issues... am i entitled to ask the buyer to pay that difference?  

[wooden_flower]

@mikedropshop 

You can not ask the buyer for more shipping $. Never estimate. Get the box and packing materials you will use for shipping, and weigh/measure the package before listing using the actual weight and dimensions.

I would wait another day at least before changing the carrier. You can change it, but some buyers have strong opinions on carriers, so I would give him a chance to say yes or no. If he still doesn’t respond, I would ship UPS and hope for the best. He can leave you less than positive feedback, so weigh the added cost against that possibility.

[mikedropshop]

ok thanks for the advice.

its hard to estimate shipping until you actually box and package an item . in my case im shipping an awkward size thing that required a time consuming custom box which i didnt want to build until i knew there was a buyer. 

what happens if I had err-ed in other direction by accident.  ie. the buyers chooses his preferred shipping method based on weight / dimensions I listed and then pays me more for shipping than what I later pay when i print my label on ebay?   im just trying to understand some things i havent been through before

[wooden_flower]

@mikedropshop 

You can always refund a bit of the shipping if you estimate too high, but you run the risk of someone not buying because of the high shipping. The buyer can only select from the shipping options you offer.

I understand not wanting to build the box, but how about weighing the item with the materials it will take to build the box? I assume this is not something you have to do very often.