Restrict appx update supersedence to limited devices ?

With reference to https://technet.microsoft.com/en-gb/library/gg682082.aspx

We want to deploy a new version of an app for testing as an update using supersedence.
How may we restrict a "Required" update to a list of devices please?

We're concerned the supersedence will mean that any new users installing the application for the first time on a new (to them) device will install the new version rather than the "current" version.

We'd rather not just set the new version as "Available", simply to avoid asking our users to manually install the update.

Thanks in advance of your kind response.