A few years ago I had my props re-pitched because I was above my WOT range of 4200-4600. I was at 4730 so I ended up going from a 18x21 with a .075 cup to a 18x22 with a .075 cup. After that I was at 4620 for some reason and gained like 3mph. So last year I had them go over the props again and add a .125 cup. My speed right now is 28 to 28.5 mph at 3450rpm and a WOT of 38.5 at 4560rpm. I called ACME props and talked to him for a while. He suggested there 18x23 with a .043 cup. He told me it would gain around 1 mph on the top end at 4450rpm and .75 at cruise. Well if you do the math, there is no way i'm spending $3500 for that. So I'm thinking...safe RPM range is 4200-4600. What's stopping me to add another 3/4 or so pitch in my prop. I would drop like 150 rpm bringing me to around 4400 rpm. I should gain better mph at cruise. I know optimal rpm is 4600, but if the range is 4200 to 4600 I should be good? right? Also would this hurt my gas mileage?