Speaking about road bikes, like the Roubaix, you want your center of gravity closer to the center of the bike. Too much of your weight over the rear and I think you'll experience the bike laboring in turns, climbing issues and not floating over bumps..more like riding a rear loader tourer than a road bike. As I read it, 50-60% weight on the back wheel is what pro riders shoot for, not to say we should worry about those figures. On the 52cm you look pushed toward the rear. Of course, it could simply be how you are fit on that bike, i.e. the saddle position.