If you use the full fizzdrop - intended for a 12 oz bottle - and the 7 oz bottles are strong enough to hold that level of carbonation, you may end up with a seriously over-carbonated American Brown Ale. Other, less ideal, outcomes appear to me to be more likely.
This is my concern as well.
The basic math for bottle carbonation isn't difficult to learn. And there are really great people here willing to help.