"Could this be the answer as to why so many of the CDS boxes have burned out."
No, that's not true. Again, to get a better understanding of how a CDI
system functions and what its' coil really does, read here:
www.systemsc.com/technical.htm under Ignition Systems.
Porsche has correctly stated that the 911 coil functions as a transformer
versus a energy storage element as in a conventional ignition system.
Therefore, as a transformer, the Porsche CDI doesn't require the inductance
of a conventional coil and can be much smaller. The conventional coil
with its greater inductance causes no problem for the Porsche CDI.
The only problem for a CDI when using a conventional coil is a coil
with a turns ratio much greater than 100 which causes too high
of a spark voltage. Porsche coils' data are here:
www.systemsc.com/diagnostic.htm