I'm starting to think I made a mistake with these two phantoms. I have the same FT02 case as you with 2 670s and my temps are out of control, at stock.
Taking Heaven as a standard, at stock the primary card hits on average a max temp of 88c and max fan speed of 87%. The secondary card gets to a max temp of 76c, max fan speed of 66. It's not the individual cards at fault; I swap their positions and those temps remain relative to their position i.e. the card in the primary position is always at most 15c higher than the other one

. Earlier this evening with the high ambient temp the primary card hit 92c, fan speed 90%. This is well too hot for me and is unacceptable. Additionally forget even adding any overclock!
I think it's down to the fact that the phantom doesn't really expel much air out of the case, but around it. That's why I'm surpirsed you are having such good temps as the gigabyte card does the same. The FT02 does a good job in directing the flow but not enough to stop one card feeding the other hot air from itself. Looking through the manual of the FT02 it states "when choosing a graphics card, we recommend models that have a fan blowing exhaust air to the rear slot, this will ensure smooth and efficient ariflow within the FT02 for maximum cooling performance". Now I know why!
Here's a question - when running SLI, does the primary card have additional work to do to cause it to run hotter? Also, in an attempt to control the temps I tried all the fans of the FT02 on max, little change. Put a piece of card between the cards, little change - but I did notice how hot the back of these cards get! I mean seriously "can't touch it for long even through cardboard" hot.
The crux of this is post is that I think to run SLI 670s you need single fan exhaust style coolers. Shame the stock cooler is so meh. Anyone have simillar or differing opinions or experiences?
I'm weighing up my options at the moment.