I think 9 is overkill because it really narrows both his calling range, and on a board that someone might be convinced to bluff, it really reduces the probability of getting bluff raised.

So now instead of having low/mid pairs with a club peeling, we are probably narrowing his range to top pairs, top pairs + club, flushes and sets.

In general I don't have a flop over-bet range. I really don't think there is much need for one. Turn I have some over-betting range depending on villains and river I definitely have an over-bet range.

I can maybe see doing this with QQ no club or something, but QQ with a club just kills his calling range to a 3/4 pot bet. We don't want to scare out pairs+clubs that we will dominate when a club comes.