I am not so sure stringing a racket bottom up is a bad thing. Especially if you are using ultra low tension like some do today with poly strings. BUT the manufacturers say the racket is stronger in the throat because of the yoke at the bottom. Also as you string the pressure on a racket moves in the direction you are stringing so it MAY BE better to string from the top down. Babolat allows one piece bottom up stringing but they recommend two piece stringing. When stringing a Babolat the long side string goes from 9T to 8T and that transition put a lot of pressure on the racket to hold that string. If I were going to string it one piece I would string it one piece I would use the pattern I shared not long ago when the long side string goes from 9T to 12T to string the top 16 crosses from the bottom up and the short side goes from 9T to 11T to string the bottom three crosses down. This allows a longer section of frame supporting the transition from mains to crosses and there is no tension loss due to tie off drawback on the one outside main.