MD3200i / MD1200 / NX3500 - adding enclosures and expand a volume

Hello everybody, happy thanksgiving!

Several questions in here but nothing too complicated.

In our company we have a MD3200i (dual controller) with 3x 1200 enclosures attached via Mini-SAS to the MD3200i, no server involved in these connections to the MD1200. This is providing block storage via iSCSI. We also have 2x NX3500 that is currently using the iSCSI SAN to provide CIFS/NFS access to a few volumes accessed from some cutomers to which the NX3500 is the front end. We need to add at least 100 TB to the current MD3200 (this is in process, we need to get the disks/new enclosures/cables first). This should be trivial to do (hotplug the newer md1200 with the MD3200i  to achieve the same configuration but with more enclosures correct? Basically what I think needs to be done is to rack and power on the newer1200s, unplug  the last md1200 enclosure from the MD3200i and attach it to one of the new ones, then that one to another and the last one of the new ones to the MD3200i, correct?).  I have read that MDSM recognized the new space automaticallty, correct? Also, do I need to stop all I/O when doing so and do this operation cold? There are roughly 90 TB (in total, counting more volumes) of critical business data in there.

Another issue is:  We need to expand one of the volumes (currently 40 TB) with the new space, but this volume says:  "Space Provisioning = Thick"  when I executed: "NAS-volumes view volume-name"  (from the NX appliance command line). Now, If we are going to expand that volume based on the thick definition this is not possible. Do I just need to backup the data, add more disk groups to the NX3500 and then create the volume from scratch? Or there is something I can do like a workaround or I can just resize the Volume?

Thanks.

EDIT: I'm reading https://downloads.dell.com/manuals/common/powervault-nx3500_administrator%20guide_en-us.pdf page 88, si I assume this is possible. Of course, 'after' I go through the process of adding the enclosures, mapping the new space to the NX3500, then discovering the LUNs. Any opinions are welcome.