I'd say 50% PG 25% both SG & SF.
I don't run RnG too much as 3-2 zone seems to stop it fairly easy, but when I have played it & I haven't had issues, shots forced to other positions, it's the PG & SG that take most of the shoots, so maybe a SG at the point who can pass maybe worth a go?
Check out River Legends (78204). He plays RnG all the time & is about as good at it as anyone can be. Watch a couple of his games, wins & losses, to see what position does what when he's scoring & when he's struggling to score & this may give you an idea of what you need.
Hope this helps.
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