9.5mm/s is a bit slow in my opinion and the coating will be building up too quickly. Coatings perform better applied in small layers (around 0.004 - 0.005" per pass) thats the rule of thumb I used to work too your employer might be different but I didnt have too many problems working to that method.
If you put the 6 inch barrel on back off the Spray distance slightly maybe to 14 or 15 " I've never used a powder with a composition the same as you mentioned but I have used 86/10/4 and 88/12 and similar and the spray distance was 14" with an 8 inch barrel
As far as the other sprayer goes, stick your foot up his back side for not keeping records