At the time of writing I've finalized a long overdue general system cleanup. To my pleasure I found it still booting properly, so it MUST somehow commenced as desired.

My system is a venerable one, an Amiga Micro-A1 in C designation. Bought it in December 2004 from Vesalia and yes, it is still 'on first battery'. Through the years I held all iterations of the OS installed and working on disk, from OS 4.0 Final upto and including OS 4.1 Upd 2. Five versions of the OS. Usefull? Hardly.
And so I tried both OS 4.0 iterations lately and found they could not cope with a filesystem like XJFS, as that one was introduced further down the timescale. The usefullness of both of them was therefore nihil as all non-bootable partitions rely on XJFS for their housekeeping. Doing away with both of them returned two rather small partitions of 164Mb each to the system. As I keep bootpartitions religiously clean of third-parties wares, I was pretty sure I could simply delete every drawer and file in both partitions, without the risk of loosing some valuable file. And as the two partitons were located adjacent I could merge them into one partition of some 330Mb.
Next to that partiton was a partition with the third iteration of the OS installed: OS 4.1, taking 210Mb diskspace, but showing a percentage of used space of some 82%. Knowing that there was quite some superfluous files located on that partition, I set out for a thourough scrutiny of all files and drawers.
I deleted the drawer 'OS_4.1:Internet'. Have never found any use for that one. It saved about half a Meg of space.
The drawer 'OS_4.1:Devs/Internet' was long since replaced by a softlink, as this saves me from setting up internet again everytime a new iteration of the OS is installed. The actual (physical) drawer is located on volume 'ExtSYS:'. The gain in space is neglectible with 45k bytes.
From 'OS_4.1:Prefs/Env-Archive/Sys' I had several #?.prefs-files replaced by softlinks to simmilarly named and located files on partition 'ExtSYS:'. This way a change in setting in one iteration of the OS is automatically broadcast to all other iterations which have those #?.prefs files replaced by softlinks. DefIcons.prefs, dos.prefs, Font.prefs, GUI.prefs, Palette. prefs. WBPattern.prefs, wbstartup.prefs and Workbench.prefs are all replaced by softlinks. As I keep all of my bootpartitions locked at all times, the added advantage is then the possibillity to change settings (prefs) without unlocking the partition.
The drawer 'OS_4.1:Storage' saw itself eradicated as there is very little swapped from and to. Some 1Mb and more space was reclaimed (actaully quite a bit more, but that had already been removed in an earlier upwelling).
'OS_4.1:Locale' was considerably cut back as the subdrawers of 'languages', 'countries', 'flags' and 'catalogs' were cleared of all redundant files. The gain was some 7.5Mb.
As a final touch the drawer 'OS_4.1:Kickstart' saw itself removed! The gain in space was here some 7Mb. The contents of that drawer had already been moved over to another directory which resides on partition 'BootPartition:' (note the aptness!).
I'm still pondering the idea of removing 'OS_4.1:Fonts'. The contents could be housed on a central 'Fonts' drawer, 'ExtSYS:Fonts' being my only candidate. It would free another 13Mb. Very tempting.

'OS_4.1:' is now located on a 128Mb partition, with a fillrate of 95%. As the three partitions, 'OS_4.0 Final:', 'OS_4.0 Final 1:' and 'OS_4.1:', used to take up some 538Mb together, 'OS_4.1:' now taking up some 128Mb a space of 410Mb was reclaimed. The upcoming release of OS_4.1 Update 3 will therefore find itself plenty of space.

Next partition to be cleaned up will be 'OS_4.1_1:', the first update to OS 4.1. With 227Mb diskspace at hand and a fillrate of 96% I feel that some of tat space can be reclaimed. I'll keep you informed.

A note on partition 'BootVolume:': this is a partition of 46Mb and a fillrate of 50%.
This partition is with a bootpriority of 3 the bootpartition with the highest priority. It contains only two directories: 'Kickstart' and 'L', the latter of which containing only one file: 'slb_v2'.
'KickStart' on the other hand, contains three files: 'KickLayout', 'diskboot.config' and 'loader'. Furthermore it contains per iteration of the OS a directory housing all the files like '#?.kmod', '#?FileSystem' and some '#?.library' entries, which are needed to boot that particular iteration of the OS. For clarity I've named those directories after the iteration of the OS they house, so 'OS_4.1' upto 'OS_4.1_3' for the upcoming update 3.Every directory contains a special file 'BootDevice', which holds only some 3 to 4 or 5 characters in the form of 'DHnnn', telling which partition to commence booting from.

As I said I'll keep you updated when time comes.