crashnburned,

My smoke unit feeds a 1-1/4" diameter stack one my Ironclad, the effect is almost what I would say true to scale. With two stacks to feed, I would go with 2 units. Only because the boat is a steam boat and a little extra smoke will give a good steam effect.

I have pondered the idea of adding a piston type air pump connected to the prop shaft. When the shaft rotates it will put a puff of air into the smoke stack simulating an exhaust of steam out of the engine. Doing something like that with twin stacks on yours would look awsome.

LtDoc,

I'm tempted to search the local thrift stores for one of those piezo humidifiers, tear it aparrt and see if it can be made into a smoke unit. If it doesn't work I would only be out a few bucks.