[O] Changing '_archive' extension to allow Easy PG encryption: "_archive.gpg"?

['Mash (Thomas Herbert)]

Morning,

I wanted to know how I would change the default '_archive' extension?

I work with encrypted org files "foo.gpg" with Easy PG and the
added header...

# -*- mode: org; epa-file-encrypt-to: ("address@hidden") -*-

But today I discovered that when I archive my TODO items they are of
course saved unencrypted to the archive file "foo.gpg_archive".

This really is not ideal situation!

I tried adding my header to the "_archive" file but this doesn't work, I
assume because the extension is not ".gpg".

Any ideas how would I change the default "_archive" extension to
"_archive.gpg" or better setup a case where it would change the
extension only if the org file is ".gpg" to begin with?

I suppose could also look to setup a case for Easy PG to work with a
different extension, but would prefer to define the change for
org-mode instead.

Many thanks,

'Mash