It's probably over 1,600 nm (assuming you don't go out and backing 400-500 nm to avoid the currents.) When you go is a big deal (more gales before August/September). The five knots is a result of the current/tacking/ etc.?

I'm assuming that you won't be going non-stop; and you've figured-in some weather window realities.

There is no question that on a truck or freighter is the more rational thing.