I know it's solved ... but just in case someone is reading this in search of solutions or alternatoves:
I added a fail safe way of installing miniroot image on the pi to be used when the community images are failing.
just keep reading the page down below the links to the community stuff.
Once the miniroot is booting I generally get slackpkg working manually and use that to install all the rest I need. slackware
Slackpkg can install whole package series much like the installer so it's really easy to go from a miniroot to a full system.
On the whole I regard the miniroot thing a really powerful, flexible and fast install method, in fact all my slacware ARM devices are installed starting from a miniroot (thanks Stuart).