I'm sayin tho! This is bull shyt! How do you do that with all the equipment and r&d in the world, lame!
The problem that I had with the Solas 12-18 was too much load for my high port 701, way too much load. I flattened it out and it is fine now. A low port 771 would be minimum for this impeller in stock form. As far as the gap, its far down on the list of "things to worry about". My experimentation never revealed enough difference to notice while riding. My flattened Solas, with its larger than stock gap, primes just like 9-15 Hookers that are nearly rubbing the stator. There may be some merit with big engines in the surf but not with small stuff in clear water.