Raid 5 Upgrading Drive Size

[FrankTheTank5]

So I currently have a raid 5 config on my server with 4 3TB HDD's. I am running out of space and wanted to upgrade the drives without losing any data. Would it be possible for me to upgrade a drive, allow the raid to rebuild, then upgrade another? I currently have a RocketRaid 640L and cant seem to find any information if this is possible. I was thinking of getting 5 TB Drives. I know there's slack involved because the drives would be of unequal size while doing this process so that's something else to take into account. My current config I only use 8TB out of the usable 8.15 but while im upgrading the drives should I run into the issue after rebuilding where I dont have enough space because of this?   

[MARSTG]

 Would it be possible for me to upgrade a drive, allow the raid to rebuild, then upgrade another?

Actually that is the recommended way of doing it. First you remove a drive and add the new one and the matrix rebuilds itself. You cannot find any info on that, because hardware wise your controller does only raid 1 or 0 in hardware, you must have the RAID 5 built in software from whatever your server is running. In theory raid5 should work like that, so you can experiment. If it does not work, just put back the drive you removed.