Chatting with a local mechanic, a shop will often chop the seatpost right before sale, so you shouldn't have to worry about this too much but if you are doing need to, Do not stress as it can be achieved! Only for reference this was for any size 51cm and https://cervelotribike19613.blogdomago.com/26253980/the-5-second-trick-for-bicycle-store-near-me