pshhh 20 lbs?
I carry more than that in books...
<img src="/ubbthreads/images/graemlins/laugh.gif" alt="" />
there is this weird competition between me and mac these days.
<img src="/ubbthreads/images/graemlins/laugh.gif" alt="" />

other than that I think you could carry 120 lbs on your back for sure, you just need to keep fit and maybe train and stuff.