You are changing the original recipe though. Graff is a cider with malty hoppy characteristics with a lower (1:4) ratio of beer to cider. As you balance the amounts of malt and perhaps hops, you will be approaching beer.
An alternative to what you are doing, in my opinion, would be to make a snakebite, or half beer and half cider. No reason to brew them together unless that is what you want x # of gallons of on hand.