Just finished one the other day, small cabin in the woods, drawn with a 6 foot vanity in a corner of the bath room. I installed the light fixture box 3 feet out of this corner, on center with the vanity. Fast forward to the trim out, the light and GFCI are off center!! I inquired with the GC(home owner) and was informed that she had decided to shorten the vanity to 4 feet, " is it going to be a problem?" she asked. My reply was no problem just sign this change order, and call the sheet rockers to fix the hole. Gotta love those GC home owners!