I have a sullivan pump. 32oz of smoke fluid only lasts about 3 mins max....but makes a lot of smoke in those three minutes. I only use one Tams tube...I can't see how two could possibly make more smoke! I tap my 2 cell ECU battery so it is running on 7.4V . (It will run on 12 volts if needed). You will note on Roy's (MolarMender) installation, that he has a shut off valve in front of the smoke tubes. You need some sort of shut off when you are filling your tank, or transporting your plane, otherwise smoke fluid will drip all over the place. No need to ask how I found that out!
A picture is worth a thousand words, so here is three thousand worth:

http://www.youtube.com/watch?v=YmRfMDzl-Wo