I am measuring our pool for a new liner and I am not so confident about the measurements I am getting. It's a 20' x 40' pool. For instance, when measuring the hopper horizontal distances I get 51" from the end and 57" from the sides to the hopper floor. The length of the hopper is a "nice" 6 ft, so I was looking for other nice numbers, like maybe 48" and 60" for the distances from the hopper to the walls. Is it normal to have what seems to be oddball numbers? Thanks.