you are exactly right and you only need about 3 times the production of the next guy and be about half an age ahead in turns of technology.
You make up for it by your wars lasting 5 turns instead of 20 and hardly losing any attackers. Plus you can upgrade your transports if you really want to since having Nav 1 and Refridgeration doesn't really make that big of a deal (you can still sneak up on most cities with 5 moves and the Frigs are the only ones who need the extra move to bombard).
And the only thing you NEED is to get your ships over to the other continent before the other civ has flight and builds fighters. That's not that difficult if you've already wiped out all of your opponents on your continent (which is usually the idea). After that production shouldn't even be an issue.