How to make an 8TB protected SHR from a 4TB unprotected SHR (Synology Hybrid RAID)?

I have a 2-bay Synology Disk Station (DS220j) with a single 4TB Drive in it. There is a SHR Volume 1 on the system. It's currently without protection but it was prepared for another 4TB drive to be added.

As time passed, 4TB is not sufficient anymore and I'm wondering if I can upgrade the DS this way:

1. Add a 8TB drive into the SHR and let it sync. The capacity will be still 4TB but now protected.
2. Remove the 4TB drive. Now the capacity should be 8TB unprotected -- is it right?
3. Add a second 8TB drive dnd let is sync. Now the capacity should be 8TB protected -- is it right?

I'd like to ask if my assumptions above are right?