To be honest - I don't think that this works.
I assume you have RAID 0, so both disks form a large Volume.
RAID 0 spreads data over both disks. If you remove 1 disk, all data is lost. Once you replace 1 disk, all data is lost.
In case of RAID 1, you may swap a disk, which will be rebuild (crossing fingers...). But you don't get more space for your volume. RAID 1 mirrors both disks, so the smaller one limits the size.
In all cases, I can strongly recommend to make a backup beforehand. It is very likely that after swapping 1 disk, all data is gone. Plan about 2 days for backup and restore...