rsync as backup for laptop to desktop external HD

[Mike]

I have for many years run backups from laptops on the local LAN to an external
USB drive attached to the main desktop machine using rsync -aH. 
The main desktop is running F8 with SELinux disabled.

In recent months I upgraded the laptop to F9 with SELinux enabled.

I have just realised that the method I use gives files on the backup drive
that have no selinux contexts... so in the event of having to rebuild a laptop
and pulling files off the backup drive the selinux contexts would have to be
recreated.

I am fairly new to SELinux but I presume that merely adding -X to the rsync
command would still not produce any contexts on the files that are generated
on the backup drive since the machine that is processing the rsync at the
receive end has SELinux disabled.

At some point the desktop will be upgraded to F9 (and later F10) with SELinux
enabled - and I am now not sure if attaching the original external USB drive
unchanged would then still result in files without any security contexts on
the external drive?

If this is the case would I need to label the filesystem on the external drive?
What is the best route to getting this backup system working to preserve
security contexts for all files (including system areas such as /var /etc ?

Thanks