Lori is also correct - it is important to be sure that one diagonal isn't rough because the horse has a medical issue.
One thing about Heidi's 2-point position - doing that has helped me pick up a very subtle lameness at times. I could always tell if Shadow was due for his Adequan shot, as he would start going very, very slightly off.
Beth is correct- all horses move a bit differently and not all can be ridden the same way at all times ! Don, you could remind yourself to not put a lot of pressure on the balls of your feet when trotting ? - just kind of relax your body & see if you feel even. Get someone to critique you, but nicely ! - Heidi