zone poker so no reads

Theoretically villain should be getting to the turn relatively capped given he should be check raising a lot against my small sizing and I'm obviously still uncapped. This is also one of the higher EV bluffs I have and block some Kx combos. The 9 also doesn't change a lot except specifically 99 as I'd expect 67 to check raise a lot as well. On the other hand, Villain has called out of the SB with no reads and given how soft 25nl on ignition is already it's very possible he's a fish and is much less capped than he theoretically should be.

Either way I think I want to barrel here pretty often. Do you think an overbet works here or something like 2/3 or 3/4 works better?