I just received a pair of Gordon Rush chukkas I ordered off of Gilt, and have a question on sizing. This is my first pair of chukkas and I wasn't sure how they fit, so I ordered the same size I wear in sneakers, an 11. Seems like a mistake as they feel rather large. Do you normally order smaller sizes for these types of things? How much space in the top of the boot should there be for a correct fit?