Ok, I managed to have a nice SDK partition, here some hints:

* mmcblk1p1 (or another sd partition) formatted and mounted on /sdk
* extract maemo-sdk-rootstrap_5.0_armel.tgz to /sdk
* create dev and mount it from real dev with mount -o bind
* mount /sdk/dev/pts, /sdk/proc and /sdk/sys properly (not sure about the last two, the first is necessary to avoid apt-get errors)
* add to /etc/apt/sources.list the line:
replace xxxxx with the exact string from your scratchbox installation.

That's all, I just checked out a my qt4 project and compiled with:

* chroot /sdk
* apt-get update
* apt-get install libqt4-dev
* cd blah
* qmake
* make

Please test and elaborate the above instruction, and provide further hints to have all automounted and working at device boot

Regards

Niko