For floor/ceiling joists I've been using 2 X 6s on 1' centers. Well within the maximum spans for the grade of lumber I can readily get. In one section of the ceiling/2ndfloor with a slightly longer span I would neet to get number 1 southern pine in order to meet the need span. I can't get better than number 2 grade here for SYP. Question: can I use 2X8's for these longer spans (which will easily meet the span indicated in span tables) even if I notch out 1.5" at the ends where they rest on the top plates? Doing so would preserve my entire upper floor on one level plane.