I was considering making / the boot partition, putting the rest in an extended partitioning.

But had vaguely hoped that the fact that the extended is seen by Linux/GParted as a primary partition might have made it possible to boot from within it - but hadn't thought about the fact that the partitions within the extended one are of necessity logical.

Thanks for the timely warning - saves a bit of time.

I'm looking forward to Mint9. The RC runs very nicely from a flash drive, and seems pretty stable already, as far as day-to-day use is concerned.