Champagne not usually completely dry. I think most people would be surprised that 'Brut' and 'Extra Dry' champagne still contain some residual sugar. You would probably be better off fermenting with the F-pack added if you want a dry wine.
If you really want a 'Champagne' flavor, you will need a second fermentation in the bottle and an extended period of bottle conditioning.
From what I've read brut champagne has 0-12 g/L of RS. So I don't mind having some but until fermentation is done I won't know what is needed.
As far as the secondary bottle fermentation I'll probably force carb in a keg. I can always add some sugar if I find the acid provided by the carbonation too much.