I'm so glad I got my SL6 in a size 52 (the recommended size for my height). The fit is so perfect with a 110mm -12 degree stem. Jumping back on the size 49 Allez earlier this week I instantly realised I felt cramped up. I ended up busting out the tape measure, and too right, the distance between the tip of the saddle to the centre of the bars was 20mm shorter on the Allez so I bought a 130mm -12 degree stem and happy to say that I managed to make it fit without extending the brake hoses.
Not ridden it yet, but it measures up great and damn it looks *f##k* mean AF!