10.2 Hyper-V VM Upgrade to 11.0

[Sergei G]

I have a Hyper-V VM that's configured with:

* FreeBSD 10.2 base image (Standard distribution VHD file)
* Diff disc which is actually running FreeBSD OS.  This machine has been
updated to latest security and kernel updates.

I would like to update this VM to FreeBSD 11 and I can't decide on upgrade
path:

* Backup and restore to a standalone disc image and follow standard upgrade
instructions.
* Upgrade in-place using my differential disc.  It seems that keeping 10.2
Base image is becoming a dead weight in this case.

Is there a better way to upgrade my setup?