Migrating OS to VM while shrinking size on disk

Ok, so forgive me if I explain this poorly.

For years, I have done everything off a single install of Ubuntu Mate, treated essentially as a home server. The OS runs on a 120GB drive, but only takes up ~45GB.

I want to install Proxmox, and do everything via VMs now. I have gotten an image of the OS drive using clonezilla. I was able to restore it to an external 128GB virtual storage, and that worked. Great.

But I want to have all my VMs running from the original 120GB drive (which remains untouched, and I've removed it from the device during my testing). Which means I want to restore the original 120GB image to about 55GB.

So it seems I have a few options:

• clone the image to a smaller virtual drive using clonezilla and this magic (I just tried this, and the transfer failed around 60-70%)
• clone it as it is, and resize using Proxmox, which Proxmox says is not supported
• shrink the volume on the original drive, then clone again with clonezilla again, and then restore with clonezilla to a smaller drive. I'm not convinced this will work, but it's the only other thing I can think of
• create a new VM of a clean install of ubuntu mate - but if I do this... how do I know what to copy from the old install to the new install?

That last option I came up with while I was writing this. And then I found the app Aptik, which sounds perfect. This might be the route I go, but I would like to know if there is something else I'm not thinking of or if someone knows of a better way?

Thanks for any help