8800GT SLI overclock, temperature concern

I've recently upgraded to the Gigabyte EX58 motehrboard and have put 2 x 8800GT on it in SLI.

While installing it I saw an obvious problem, that there was no gap between the 2 8800GT's and therefore one of them was going to get very little benifit from its fan.

I've had a look at overclocking, but even before I overclock I see GPU0 hitting 87C after 5 mins of the ATI artifact scan. GPU1 remains solidy around 50C.

I've done mild overclock of both GPUs to 690/1725/1050 and after around 10 mins of artifact scan GPU0 hits 91C, while GPU1 remains at 51C

Is this something I should be concerned about? 91C seems pretty high, but I get no artifacts at all, even if I take it above 700Mhz.

I guess the fix could be to split the cards and buy a longer SLI bridge, but the motherboard manual suggests using the 2 PCIe slots that are right next to each other.

Also, I'm using RiverTuner. Am I correct in assuming that RiverTuner automatically adjusts both GPUs at the same time?