Could be what your getting with the fan WFO and being more than 6" off panel is a fog. Iwata's want to be up close and personal and "if" you prefer being off the panel further,you'll get the o'spray so some fan shut down is necessary. Along with the psi being over the 16-18 recommended and the fluid cut back some,you'll blow out the middle. I've found the recommended is a "guess" with most air set up's. Until you've used an air cap guage and actually SEEN what your spraying at,you could be off,a LOT.
I found that i needed 20 for the 10 at the cap with MY air set up so some testing is definetly in order for a good pattern,so just because your setting it at the "recommended" does not mean your getting what's needed for the gun to spray "right" or at least the way IT is designed to spray and this is kind of a fault with Hub IMO as air supplys DO differ and he really does not address this issue as much as he should. I was NOT pleased with the way mine sprayed base at the "recommended" and after checking with the cap guage,finally understood "why".