Yes, I'm left handed. Knee pad on my left leg. The main problem I have is that, in common with a lot of lefties, when I write at a desk or table I have to rotate the paper to the right by about 30 degrees in order to see what I am writing. That's fine when I can move the paper but with a 'straight' knee pad and the paper held by the clip I can't rotate it so my writing ends up slanting across the page. Very difficult to be organised! I would like to try rotating the knee pad to align with my writing.
I would be interested if other lefties have the same problem!