For creating the bootable usb stick:
When the installer appears, wipe the disk, then select customize. Keep all default, and in addition select:
- PCIRootUID = 1
- Atom kernel
and maybe something else too, I went for the minimum because encountering errors.
After installation boot back to the installer, open terminal, mount -uw / and replace the installed system's AppleACPIPlatform and IOPCIFamily kexts with the ones used creating the usb. Also put LegacyAppleRTC.kext (first google result) in /Extra (this fixes the RTC: Only single RAM bank hang) and repair all permissions. It should then boot up from hd.
Notice: for me it seems not to work if you copy the kexts from the installer usb's SLE. Put them to usb root and copy from there.
So far no networking (any kind), no sound, no touchpad/keyboard, no graphics driver (resolution is fine 1024x600x32 but no QE). Instead, my memory is now showing up fine (2Gb 1333MHz DDR3) which was 667MHz DDR2 in S3v2.
Now I'm doing a fresh TM backup of this system, just in case.