Did you defrag? Perhaps the 6981MB that PM8 will allow you to move is the contiguous block at the end of the partition. Since Disk Director includes a disk de-fragger it's probably factoring this into the conversion.
Edit: Never mind, I guess PM does a move then it resizes also.
On the question "is it safe?", any partition sizing is potentially dangerous. I've used Partition Magic in the past, and free stuff like FIPS, and have had successes and failures.
