I know for a fact that 915F fairways are 0.5* flatter vs 910F. The spec for the 15* fairway at A1 on the 915F is 56.5. That for the 910F is 57.0. The 913F doesn't have its lie angle specs shown. The way I set up my 21* fairway for the 910F is C3 with a 75g shaft and 41". I have to set it to D3 on the 913F with the same shaft length and a similar shaft (Diamana 70).