I would have a few local experts take a look at your boat - a surveyor, or even a naval architecth. Lots of people make changes to thier boats that effect the performance - adding ballast removing it would be an example.
I wonder how much effect 12" off your mainsail at the the masthead is going to have. Yes,the CG will raise a little bit, but if your boat is already stiff....
One good way to see what it will do to the asthetics is to find a line drawing of your boat, scan it, and then make the changes there to get an idea what it will look like.
Faster may well be right, but you really do need to have someone actually look at your boat that has experience in this type of thing.