Ruck

What is the best amount to put in attack and defence ruck when playing a passing game please.
I know I always say this, but this time it's actually more true. It depends on your player ability, the number of players in a ruck and also critically depends on your opponent's settings. There are also some neat intricacies that you can find if playing around. It reminds me a little of a Bible verse that tells us that the first will be last and the last will be first. I have now said too much and not enough all at the same time.
Riddles!