Mitchell,

In regards to our SureFit Tour Hosel, the loft differences as you move up and down on the grid are .75*.  Ultimately adjusting a 9.5* down, we would get to an 8.75* loft where as moving the 8.5* up, we would get 9.25*.  Besides the small difference in loft (effects the spin rates approximately 250 rpms per "click"), there is a small difference in the face angle at the address position.  The SureFit Tour hosel allows you to independently adjust loft from lie, but not loft from face angle as they are linked.

As soon as you start adding loft to the 910 series of metals, you actually close to the face (and the reverse when you decrease the loft) which results in a slight change in flight characteristics such as trajectory.  This really helps the fitter dial you in to a driver, fairway or hybrid that will help lower your score. 

To shed light on your question about the difference between an F and Fd, the 910F delivers a medium trajectory and mid-low spin while the 910Fd is optimized off the tee with mid-low trajectory and low spin for a more boring ball flight.  The 910Fd has a Center of Gravity that is higher and closer to the face than the 910F producing these lower launching, lower spinning shots.

Ryan P - Team Titleist