Jack,

One of the things you wrote was:
<... I am not sure that the Unison system is a real solution.>

Surely you mean EPIC for Lycomings (like FADEC for Continentals).  If so, I
agree that much needs to be resolved.  PRISM does sound like a more
technically correct approach for the future fuels.  However, today, LASAR (a
Unison product) works quite nicely with 100LL and the backup is decades old,
magnetos.  Personally, I am looking forward to a 300 HP, liquid cooled Rotax
working with a future no-lead fuel..

Scott Krueger