Hi,

Why not try it with one and see how you like it? Adding a second spray jet isn't a big deal. Personally, I don't see any difference in any of the smoke systems' performance, so I opted for the most economical, yet reliable system. I installed the TME Simple Smoke pump with one sprayer jet. It uses a 6V Rx pack and works MARVELOUSLY! I tested it yesterday with a Yellow F-15 (split exhaust) with a P-120. On the ground, the smoke seemed to come more from one side, but in the sky (yesterday was a beautiful, blue day), it looked like it billowed from both. I use a 1/8" inside-diameter tube on one side of the engine.

The system: $99 from Horizon.
The metal tube: $0.60.
The section of neoprene tubing: $1.00.
The section of tygon tubing: $3.00.
The battery pack: lying around.
The pride of D.I.Y. system setup (2 hrs), D.I.Y. smoke tank construction and the satisfaction of having AWESOME smoke every bit as good as systems costing twice the money: PRICELESS!

Like CARS said, if you have smoke coming out of the back, you're happy. Good luck with your project!