Hi,
You will need native firmware to carry out back to back flashing as here to avoid "aegis issues":
https://talk.maemo.org/showthread.php?t=89345
Hopefully you are going to use Linux to re-partition, but suggest look at these resources:
https://talk.maemo.org/showthread.php?t=91914
http://www.thegadgetfreak.net/2012/0...ioning-n9.html
Getting partitioning sorted is probably the hardest if unfamiliar as after that just following commands upon device: https://leste.maemo.org/Nokia_N9

Some of links now outdated and you may need to look at Paragraph 6.4.1 here if you end up in MALF state with device:
http://wiki.maemo.org/N9QTweak or https://wiki.maemo.org/N9/N950_Rescue_CD

This user wanted to install Maemo Leste upon N9 16GB in this thread:https://talk.maemo.org/showpost.php?...0&postcount=42