Adding more partitions to my HD is exactly what I don't want.
When I'm done with all my testing and the final size of the disk image
is sorted out, then an extra partition would make sense.
In that case I would eventually prefer a bootcamp partition, but well,
Parallels support is still limited, since you cannot boot while you have
an external Windows drive attached...
Anyway, saving stuff to a different location might work, despite the
fact that I don't know how to avoid killing my existing file when restoring
with SD from the backup - probably also not possible.
But many thanks for your quick answer - Parallels are an order of magnitude
slower
