There is no doubt you will have a noisy overflow. If the aquarium is in a room were the noise doesn't bother you. Then what you have is ok. If it does bother you, you have 2 choices,
Durso standpipe, or add a ball valve between the overflow & sump. Close the ball valve back just enough to back the flow up over the 3 1/2in pipe you have now.
Be warned everyone will bitterly argue against backing the flow up with a ball valve.
I skipped the durso standpipe & backed the flow up with a ball valve. I've had my system this way for over 6 months without any problems. Why everyone argues against it, I don't know?
Like I said before, I'm just adding food for thought. The choice is up to you...