I believe that if you look at the stock pipe arrangement (the TOR arrangement too) from the rear of the bike, the left side single pipe is pretty much "centered" (height wise) to the two on the right. Even if you were to get the cat bypass modifed to adapt another pipe, the balance you desire would not be clean cause you would need to alter the single left side pipe in some way to position it either higher or lower, which ever, to allow the additional pipe on the left side. Then, as stated by another captain, you would need to fabricate brackets to affix both left side pipes.
Lots of work! Great results???