don't bother.

Smoke systems on engines smaller than .61 ci 2-stroke, or smaller than .72 ci 4-stroke just don't put out enough smoke to be worthwhile. the small muffler volume, and low heat of the exhaust (low volume of hot gas) make it virtually impossible to get a good smoke trail going.

The equipment for the smoke system takes up room and adds weight... both of which bother the smaller planes more than with something that already weighs 9+ lbs.