Thanks for your reply Jan.
You are modelling a different behavior than I thought then. What you explained could happen if the (engine-driven) fuel pump was to weak, that's why I said I would go see a mechanic
. Fuel priming also wouldn't help in that case, an additional electric fuel pump would help though, but the Cub hasn't got one. The common reason why airplane engines stop at low gs is because the carburetor isn't working then. Happens all the time when flying aerobatics in a Robin 2160...
Regarding restart, you are absolutely right, you need quite a bit of airspeed to overcome cylinder compression. In the RF 5 (2.0l Limbach engine) it is about 200-220 km/h, as you can see here. It is a handbook method in a TMG like the Fournier.
In SEP-aircraft you are usually not allowed to kill the engine on purpose (at least in Germany as far as I know) but in the Robin 2160 (Lycoming O-320) the propeller will come to a complete stop in a few turns of a spin. It restarts at around 250-270 km/h, or using the starter of course.
Again, thank you very much for continuously improving aircraft physics in the sim!