How can I redirect storage of Multipass VMs?

I've just been trying out Multipass and can see great value in using it for training and testing. Unfortunately with the small SSD I use as the root volume in my server it quickly ran out of space.

I can't seem to locate the path where the disks are stored and it doesn't appear to be configurable. Is there a nice way to use a custom path for VM storage and image storage?