FYI have been successful in following RobH's ideas, mostly.

Other things I tried:

-gnutar-ing the running system (the whole disk - mucho MB's) does not work as some files are active and even root cannot access them.

-stuffit/gzip from OS9, and replace from OS9 - will not boot when extracted.

-disk image of OS X disk, almost works (boots) but you cannot see/access other partitions (probably to do with invisible files)

Additionally when following robh's instructions be careful to NEVER transfer the .tar.gz file to a HFS Standard disk (dont know what it does but something breaks), HFS+ is fine.

A better way to transfer Apps and Finder based packages and installers is to use OS9 to create a HFS+ disk image (OSX Disk Copy cannot create), mount it under OSX and copy everything onto it. So long as you don't mount it under OS 9, you can run all apps from it with ease (a good alternate to partitioning your hard disk in preparation to upgrading to OSX Final).

I have heard some references to Apple providing a Software restore tool for OSX (like OS9) that uses Disk Images, and given my experiments I think Disk Images are going to be another Apple un-sung hero-technology (I have started using it instead of Stuffit to create software drag-n-drop installers for delivery of software via FTP).

Hope this helps others.

here is the Apple solution to do backup cd - they call it restore CD- you can either do a simple Backup volume or a bootable one. It requires some scripting additions disc copy 6.3.3 and others little things. You need ASR (Apple software restore) too.
You can find it on your "restore"CD shipped with your Mac, or any install disc (9.x)

the apple hint is here. I'm gone try that before upgrading to 10.1.
And as I have a superdrive, I'm gonna save all this on a DVD. hope it works.


http://developer.apple.com/testing/docs/TNasr.html

By the way I've changed quite some stuff in the finder such as menus, systems icons, login panels, about box,etc… I am wrong thinking the upgrade will erase all this. does a copy of my actuals 'touched' ressources would be enough or is it a very big upgrade so I'll have to redo everything again ?