Rutan around.....
Good work there. Clearly not rutanaround at the back of the class were you. Unlike a couple of other ppruners
deadstick
The shorter latency of mogas Vs Avgas means that the peak pressure is higher and so is the CHT. Neither of these things is optimal.
The spark timing is fixed at 25DBTDC and being a direct coil on the flywheel system this will mean the spark (in theory) will fire sooner than that of a conventional magneto, but only a little. It could be said that the plugs location partially offsets this, but I do not know that for sure. (Flame front propagation).
High CHT, poor fuel quality, and with MOGAS there is not guarantee, there could be increased peak pressure and thus CHT. Add to this induction leaks and or the ordinary fuel distribution and how you know what was happening.
My suggestion is that with Mogas compared to Avgas all things being equal, you had higher CHT and lower EGT.
There is a large difference in Octane rating. So specifically which Mogas were they using and from where?
So getting back to the failure with a rapidly rising CHT and the two instructors on board, have you any photo's of the failed cylinder?