OK,
So I know that some folks simply like a rose or blush. I would, however, like to let my own tastes dictate the following advice. If you are "on the fence" over rose, then continue reading. If you are a big fan of rose, then please disreguard this posting...
I would advise you (in the strongest way possible) to NOT make a rose. If I understand things, you plan on blending a San Gio with a Sav Blanc. These wines are so wonderful on their own that I am afraid that blending would only produce something far worse.
A san gio is such a classic red that it can rival the best of the French vinifera. When all goes well, San Gio yields a soft, subtile, wine that offers a wide variety of complex flavors and a great tannic structure.
Sav Blanc yeilds a very sharp, light, and crisp wine. It is (IMHO) the polar opposite of a san gio.
Why blend them?? I know that there is a spirit of experimentation, but why make the effort to avoid making a classic red and a classic white to, instead, end up with a rose? If it were me, I would make a sav blanc, and a San Gio sepperately. If you are truly curious, you can always blend them together later as a bench test.
I would at least recommend that you choose differently in the grapes you have selected. I would replace the Sav Blanc (one of the most acidic white grapes) with one that is much softer (say a riesling). The Sav Blanc (being so acidic) would bring sharpness and crispness to your rose that is not really what most people look for.
Again, this is only my opinion and I am not saying that other opinions are any less valid. I hope that I did not offend anyone here as this was not my intent.