We're upgrading a cabin and decided to put in pine flooring to match the original flooring. Problem is that there is a dip in the floor. Joists are 2' on center, and there is a drop of about 1/4" to 1/2" between two of the joists. We plan on running the flooring perpendicular to the joists. So my question is, how level does the floor have to be? What problems might I have if I run the flooring over this?