Have wondered. Pads have a water-proof backing, but inside a diaper, any leakage would go to the diaper, right?
One idea i haven't had to try, as my problem is reduced (right now, anyway) to only need light pads, is: what if the pads were placed at the outside edges where the leaks occur - on the legs, say – to catch what escapes? Very temporary, need to be changed out, but that might help. Try it at home, first, see what happens.