Thank you!

So, i found an App (Mount2SD) which, at boot, tells me there's no boot script, and asks me if I want to create it. If I say yes, some too fast on-screen messages prevent me to fully understand what happens, but one thing I see is that it puts the script in /system/etc/init.something . As I get there, init.something turns up to be an empty directory.

Also, the same App shows me the mmcblk1p2 ext3 partition, and it says it is unmounted. No option to mount it. Only to "move apps to SD", which I don't want to do just yet.

The system already has an option (an App, actually, APK Install) that lets me choose where the Apps should go. If only I could point it to mmcblk1p2 (once mounted)...