While testing existing fileservers I found some problems (9legacy) :

1) paqfs :

Using a partion written by "mkpaqfs -u" as a root-fs with paqfs leads to "Bad Header Code" / "Bad Trailor Code".

Are the current versions of mkpaqfs and paqfs incompatible ?

2) kfs/kfscmd

The manual for kfscmd lists "noauth" as a command.

The current implementation doesn't support "noauth".

3) bootdir size limit

When adding files in bootdir (kernel) there exists a size limit. After reaching this limit the processor resets and the boot process restarts (bootloader : nboot/9bootfat, ...). 

I found this limit by adding raw files and testing for my configuration. It would be helpfull for others to mention the max size of the kernel image.