The main problem with the small plug caps is that people don't always install them correctly but they work OK otherwise. I agree they are a source of problems for whatever reason though mostly just misunderstanding about how they should be installed. Some of the small caps require a 1/8 turn to lock where some others just push on. Then there is the problem of where to stuff the ignition box in an othewise small airplane. Small, under 20cc engines are great for people that already have gas experience but going with small gassers can extend the learning curve time for those moving from glo to gas. I consider the smaller gas engines more of a novelty than a reliable power source. Great for people who like to tinker with engines. We have some excellent glo engines these days and other than the fuel / oil mess, for under 20 cc engines and as Speedracer suggested glo is probably best.