QDM,
Remember the Coffmans well from Chipmunk days.
Not the kind of thing you could sit and make on you kitchen table !
Seeing rows of a dozen Chipmunks all starting up to be ferried to the University air sqadrons was like WW III !
The breech held six and we would stand by with spare breech barrels ready loaded.
Problems were not only the engine not starting ( too weak or too rich) but dud cartridges that gave smoke but no fire
There is a conversion from Coffman to electric but may no help if you dont have an electrical system
