DisposableVMs effectively have **two** templates.
There is the qube that is the template for the disposableVM - that is a
qube that has the `template_for_dispvms` property set. This is called
the DisposableVM Template.
Then there is the "normal" Template that *that* qube uses.
I think that David was suggesting you edit the qube that the
disposableVM is based on this is what you did.