Size is not bad - Although, I'd still like to see it made for twin 55's. Why not R&D another with the twin 55's? Then you can compare the 2 for preformance.
It's just that - while the 75 is a nice size fan - you need to run 3S at 60 amps!!
or 4S. When the 55's can run a 3S or 4S in a 2100 size. Makes it cheaper! Maybe easier too as lots of people have this very popular size of lipo.