Did you have a bigger than standard brick? The T520 used the standard Lenovo 90W brick which is really pretty compact -- the 65W that is optional with the X1 Carbon is not much smaller, and it comes standard with the same 90W brick that the T series uses. It might have depended on which GPU you bought the T520 with -- my recollection is the ones we evaluated were "big CPU, integrated GPU only."

There is a 135W brick available for Lenovos, but at least the equipment of the T520 that we bought didn't require it -- that was the brick on the W500 and W510 (the W520 and W530 required an even bigger 170W.)