Seeing as you flopped a hidden straight and there are no flush draws you only have to fear someone with a set filling up. There was no PF raise so I imagine you have a smattering of draws and pairs and overcards. I would raise it to 4.50 or so here. You don't want to get counterfeited and if anyone has a real hand (like a set) they will probably reraise you here in which case you can just call and take a card off. If you take the pot down awesome there is already $5.50 in it. I bet you'd get at least 1 caller and you could bet 3/4 of the pot on the turn depending on the card