Part II :-)
Go into share/matchbox/vfolders
there are 5 files, 0001.directory to 0005.directory. These hold the settings for the tabs, including names and icons.
I now have Internet - Work - Media - Games - Settings (with appropriate icons) on my tabs :-)
Backup everything up to my SD so as I don't have to re-hack it next time I brick it (and there will be a next time :-)
Guess the next thing is to track down the metrics and make room for more icons/more tabs :-)
Oh, yeah, a friendly footnote to anybody making up packages, please leave the ItemIndex setting out, makes it so much more user friendly :-)