I think you get encumbered at 2/3 of maximum, IIRC.
at >75% <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />
is that the RPG norm??? I could have sworn most RPGs it was 1 OVER the max. Perhaps a color coding system of sorts to alert you when you are near encumberence would be an idea.