Storage Spaces Direct (S2D) How Upgrade Cache SSDs?

How would you go about upgrading the cache SSDs in an S2D Cluster?

We have a 3 Node Cluster with 4x 1TB SSD and 8X HDDs in each.  We want to upgrade the existing SSD for a new model. 

We want to know

1. Can this be done efficiently without downtime for the cluster?

2. Must the same number of SSDs be used, ie can we replace the 4x 1TB with 2x 2TB?

I see info on how to replace a failed disk, or add disks to a cluster.  I was not able to find anything on upgrading a group of Cache SSDs or Storage HDDs. 

Thanks,

Todd

Todd Hunter