Wait! There may be no need to reverse those top front fans. Besides, reversing one or two top fans may simply create a short-circuit air flow pattern in the top of the case.
I fully agree that you need a small positive internal case pressure for dust prevention, but you may already have that. By fan count alone (NOT a full answer!) you have four intakes and three exhaust.
TEST first. You need a small smoke source, like a smouldering incense stick or a cigarette. Set the system running at idle. Move the smoke source around the outside of your case near cracks and possible leakage sites, and observe the smoke flow. If it drifts slowly AWAY from your case you have small positive internal pressure. If it is sucked inside slowly, it's negative. If it flows fast in either case, the pressure is higher than needed. Now repeat with a higher workload, and maybe again at some max workload. If you find your pressure (by smoke flow pattern) is OK in all workloads, you do not need any adjustment.