Just a little info really:

I spoke to techies at Antec and asked the question how do I connect a graphics card with two power sockets to a multi rail psu.

The answer given:

use the two red outlets for best power

The answer actually means that rail 3 and rail 4 are both connected to the card.
So it seems that one can parrallel two rails for more power but do you know what? I'm still not absolutely sure of this!!