Yeah, I think that will work. I think that for single-drive units, the Mk1 and Mk2 are partitioned the same way. Give it a shot, let us know how it goes.
Each unit may boot very very strangely or not at all until you flash them properly. I recommend simply not applying power to each one until such time as you are ready to flash it, then:
- Leave the unit power unplugged.
- Run the .upgrade file.
- When the upgrade asks you to apply power, do so.
That should give you the least amount of trouble.
If something goes wrong (Mk1 and Mk2 are not similarly partitioned), the worst that could happen is that you need to run the builder .upgrade file to wipe the disks and then you re-load all your music. Not a big deal.