There are a couple topics on this: 1. bottom up compared to up bottom can cause a change in the sweet spot of the racquet. So with a bottom up it can change the sweet spot to higher on the frame 2. simply preference and machine, my old machine i did top bottom because i felt it played better 3. its "safer" for the racquet to do bottom up rather than top bottom. There have been reports back then where ppl break racquets during stringing doing top bottom especially high tension stringing. This is just by other's report and not proven

head heavy but not as heavy as the 99pro and 88pro series, stiff shaft but not unforgivable (more stiff than the original 77). The hitting feeling isnt as solid as the original 77 but sharper