Nope, I built 16-20 juggernauts depending on how much income the country is getting.
Like I said, using two cards in one country. Production slots or queue per turn is dependent on the income the country is earning. If you use the 200% (making the income to 16) or 250% (20) you could build up to a maximum of 20 units in one turn.
I'll try what you've said about capturing the enemy capital.
