Mike,
If you add a T to that Bane, or even a Wye, you would NOT be increasing the airflow, but would be increasing the lift, as you are not adding another 2" opening into the recovery tank itself, but rather pulling from the same 2" opening from the recovery tank.
Gentlemen:
This CFM and LIFT can be a bit confusing, but one thing is for sure. CFM and LIFT figures for 1-1/2" hose, and 2" hose, are not equal concerning the actual water extraction process, because the 2" hose will move a higher volume of air/water, than the 1-1/2" hose can, per minute.
Since recovery is the main goal of a vacuum system, the 2" hose will make a substantial difference in your recovery rates, which translates to quicker drying carpets, and more vacuum available for the wand, at greater distances.
Adding a vacuum booster, as Ed mentioned, is also a great idea, especially when it is used closer to the cleaning wand, and it is designed for 2" vacuum hose. (The booster should also run parallel to the main vacuum system, and NOT in series). That gives the vacuum system a "vacuum boost", close to the wand, where it matters the most.
Best regards,
Bob Savage
SAVAGE-1 truckmounts