I think I would just check here. You have the flush, but your two hole cards are pretty low. Got to figure that anyone else holding two spades is going to beat you.

It got checked around to you, and the pot is a good sized one. If you bet and someone comes over the top, you would have to think you might be beat and could consider folding. Or you have put more money into a pot that you can't win.

So I would say just check and hope your flush holds up. If it does, you take down a good sized pot. If it doesn't, you are glad that you didn't put more into the pot. Betting another 10 or 20 of your stack and hoping for a caller doesn't seem like a good play to me here.