For the Ender 3 I opened the outlet to 4.5mm (from 2.5) and widened it by 2.5 mm from around 12.5 to 15.0 mm) by adjusting the source sketches provided.
There is still 2.5 mm between the bottom of the nozzle (or build plate) and the bottom of the cooler. Beefed up the mounting tags whilst I was at it. Thanks Stefan for a great design and supply of the Fusion 360 file to begin with.
New version added with additional air guide
CNC Kitchen riginal file here:
Just a bit of clean up required