Just remember that the default LVM pool setup in R4.1 is different than R4.0.
IIRC…
Under R4.0, one VG, one thin pool, dom0 LVs are simply siblings with VM LVs.
Under R4.1, one VG, two thin pools, dom0 LVs in one thin pool (smaller), VM LVs in a different thin pool (larger).
Also, under R4.1 the thin pools are not set up to consume 99-100% of the VG, but less.
The thin pools are, however, set to autoextend their sizes into the unused space in the VG as needed. This allows them to grow separately.
The purpose of this change was to ensure the likeliest case of VM LVs growing too large and leading to thin pool failure will not impact the ability to reboot qubes into a working dom0 environment since that is in a separate thin pool.
However, storing large amounts of data directly in the dom0 filesystem could lead to the dom0 thin pool exceeding the VG and leaving you with an unbootable system.
My recommendation is not to store large amounts of data in the dom0 filesystem.
B