Doesn't matter ... whether you want to use the slot to maintain order or if it is the only one ... it won't make any difference.  Just make sure to force it offline before removing it for replacement.
Running an older PE 2950 with a RAID1 and RAID5 volume using a PERC5 controller.  On the RAID5 volume, 1 drive is listed as predictive fail.  However, the RAID5 volume is not in degraded mode.  I did reseat the drive, which forced a rebuild of the RAID5 volume but the predictive fail did not change.  I have gotten another drive to replace the bad drive.  Can I simply swap the drive while online or should I add the new drive as a spare for the RAID5 and then remove the bad drive? Thanks for any input. Ken
Predictive Fail on RAID5 HD and Suggested Replacement Method