I agree with both of the below. When it came to our initial Navy, we had to go with quality over quantity. In fact, one British Admiral felt the U.S. Navy was 'cheating' because our frigates had more guns and other stuff because we couldn't make many so we made the best we could.

So yeah, cap on 6, and then build normal frigates.

Adding on to what Flashman said below. The unique unit should read something like this instead:

"Constitution-Class: Replaces the Frigate for John Adams's America. Set at a 6 unit cap and slightly costlier than the unit it replaces, but moves at double speed in Coast and begins with the Targeting I and Armor Plating I promotions."

Then it would be balanced and historically accurate. Otherwise than that another mod for unsung presidents on the United States is always welcome.

Actually, American frigates were both more powerful and faster than their contemporary counterparts. Maybe they should be more expensive? Or to reflect American politics relating to the navy, perhaps limit the number that could be built?
One of the big issues during Adams' presidency was the Alien & Sedition Acts, although how that might be rolled into a mod I have no clue.
Anyway, thanks for the mod!

i can make the flour mill in some cities without rivers

JOHN ADAMS intro theme INTENSIFIES . . .

John Adams? In Civ 5?

I know him!

That can’t be!