This is my design for a comfort grip for the RG40XX H.
This design allows you to hold the device with almost no pressure on the grips, as the grooves "just fit your hands", and it positions your thumbs over the D pad and buttons.
Should fit most sized hands, unless you've got big old "meat paws" or itty bitty hands..

I designed this in three pieces for ease of print, although you will still need to use Supports "everywhere" (Print as shown in the images). A little clean-up on the bottom of the grips where the supports were is going to be needed.. I just used 300 grit sandpaper to get a nice smooth finish, but with some texture left for better grip.
Once printed, just superglue the Paddles to the Holder, they fit snuggly into the corners (try a couple of test fits to see where to put superglue, and where not to put it)
I hope you like this design,, as it took many hours (and test prints) to get it just right..