Bigger fans should work. But it will be louder and hotter then the 106-100
The specs they list are really pushing the cards 4500/16 = 250 watts plus per card.
My gut tells me set a tdp of 200 watts and you will do 3200 plus 300 = 3500 watts and still be over 9000 sols
WRT the fans we will test the existing 12 x 120x120x25mm 3400 RPM fans with PWM speed control vs 6 x 120x120x38mm 4500 RPM fans with PWM speed control to determine the relative thermal, acoustic and power characteristics of each config. The best combo shall prevail.