Just wanted to report that I've been successful. As my bootloader was still intact, there was no need to replace it. Using Windows TFTP server SolarWinds, treating all file access permissions correctly without any manual intervention, I could easily transfer the original kernel to my DockStar. Taking some hints from
HERE, I finally decided
NOT to involve the initrd portion in my recovery procedure which was a very good choice. I just flashed the redstone kernel, nothing else. Now I can boot into my original PogoPlug environment again which fortunately retained all my previous changes and settings. From there it will be no problem to re-install a new ALARM system to my USB stick.
Thanks sambul13 and WarheadsSE for pointing me in the right direction.

If you don't mind I'll mark this thread as [SOLVED] so that it can be closed.
Regards,
BillyBoy