You could try also this:

• Create a Poly cube,
• Convert to SubD,
• Open up a second Perspective window,
• Space-click Poly proxy (or something don´t remember the name exactly) in one of the windows,
• On that window click Show and uncheck SubDs,
• On the other window click Show and uncheck Poly´s.

You should have two perspective windows, one with a poly cage, and one with the subdivision updating. No need even to create instance copies. All done with the same object.

Thanks for writing the PM Howard, I´m currently looking how we could approach the tutorial idea.