What is the engine, some of the ones that they suggest a buzz coil for do not work so well on a single spark, the buzz type proveides a series of sparks over a longer period of time which does suit some of the slower running designs.
Watch some of the RC engine ones as they often have auto advance and get confused ifused on teh timing gear of a 4-stroke rather than straight off the crank of a faster reving two stroke.
I mostly use the ignitions from S/S in the States but teh small cdi from Minimag here in teh UK is said to be good.