In Summary My Comments/Suggestions are:

• You've picked on the right one to try to copy - Borg was absolutely amazing.
• But he did have two backhands. His backhand up the line he kept two hands on the racket, but the ball across the court he used what i call a three quarter double handed backhand.
• What he did was he took it back with two hands, he brought it towards the ball with two hands, and on impact with the ball he took the left hand off of the racket and he finished with a single hander. But he did have two.
• In certain situations you will find that you can use the two handed shot but that generally speaking the three quarter one will suit you better. But I guarantee that the three quarter one will be better than the single one.
• Of course we have a wonderful fellow at the top of the game at the moment who uses this single hander and i suspect that you might be influenced and want to go back to it. Its a genius of a shot that Federer has and i suggest that you aren't quite in that category and should stick to a three quarter one.
• Best of Luck.