I’m curious about how any people have customised their numpad layer. I ended up deciding on a toggle for that layer rather than a lock, mapped to the right palm, and ended up shifting most things down a row (and added a few things):
This made things much more comfortable for me - I felt like I had to move my hand up a row when using numpad, and that was a pain but the alternative was overstretching for 7, 8 and 9. Now I’m a lot more fluid with it. The forwardslash falling naturally on the pinky is also something that has worked out very well.