Have you adjusted the Idle stop screw?
make sure it holds the barrel open .5mm-1mm
20% with a #8 plug should be fine

Are you sure the clutch isn't binding up,,,that's a reason for engines stoping at idle too

Go ahead and use the factory settings for the .21,,that will be close enough
they are always on the rich side anyway, so don't be afraid to lean the low speed neddle a little at a time until it will hold an idle, just keep an eye on the temp,,don't let it get to hot