On the opposite site you can mount the external fan and could do away with the need for an exhaust chassis fan, possibly.
The central fan refitted. There is plenty of space for air flow and fingers if needed. A four pin PWM for both fans means good management of power and noise.
With the second fan fitted, it covers the memory slots if mounted on either side. We have used Corsair Vengeance LPX DDR4 modules for this test, they have a slightly higher than normal profile.