Pascarelli’s Book has a good chapter on when and how to do strengthening exercises to combat RSI or Carpal Tunnel Syndrome by using weights. He does not talk about size of weights to use when weight training.

When I started his program, I started with very light 1lb dumbbell weights and slowly moved up increments after many months of therapy. I have been doing these weight training exercises every morning for years.

As usual, consult your doctor and hand therapist for advice on weight training.