Just ran you're numbers through my trajectory profiler and at 95mph swingspeed with a 9* driver you'd need to swing upward at about 10* more to achieve the necessary 18* launch angle to pick up an additional 10 to 15 yards more carry (this is assuming you swing straight thru the ball and not upward). Before you spend any more money on shafts I highly recommend you seriously look toward a more lofted driver (12* or more). The added loft will have more affect on carry distance than shaft flex.
As far as overall club length- longer clubs can mean longer drives, to a point. You might find that a shorter (let's say 44" or less) overall length might actually work better for you as far as overall driver distance and accuracy. I swing my 44", 9.5* drivers at 110mph on average with consistant distance and accuracy. Anything longer and I'm losing it all over the place. It's not just the shaft that matters, it's matching loft and shaft flex with your swingspeed/tempo/wrist release than makes the fit.
Find an experienced clubfitter in your area and you'll never buy anywhere else.
Good luck in your endeavors!