I'm installing a pedestal sink and come across a problem with the 2 pieces. The floor is level...the wall is plumb...but when I dry fit the 2 together and slide it into to place there is about a 1/2in gap between the top back edge of the sink and the wall. If I rock the sink back so it's flush against the wall... then I get a gap between the bottom of the sink and the top of the pedestal. I'm starting to think I have the correct sink but the pedestal isn't the matching piece to the set since everything is level. Any suggestions?