I understand the need to monetize BOTH the print and digital versions of your magazine. However, you have bought into the trap that is killing traditional media outlets - Overvaluing a digitized version of a printed/physical medium. I know that it requires additional time, work and money to create a digital version of a printed magazine.
As a subscriber of the printed version of your magazine I should have FREE access to its digital counter part. A digital only subscription should cost less than print (20-30% at least - hell that's at least the savings from postage). If your digital versions offered priviledged access to premium online content a modest additional fee might be reasonable (it needs to be less than the 33% premium of your "Combo Offer").
It would be easier to swallow your digital TAX if it also provided unlimited access to your digital back issues and reviews
Please reconsider -