there is no static limitation in the miner - from that point of view it should work with 8 GPUs. Can you please try with a lower intensity? In the beta you check the 'auto optimize' function is active if you do not add -i or -gs to the command line. It might be that I use too high values for optimization in this beta. So please try with -i 14 - just to see if that works better.
Please let me know - I will take a deeper look into it.
Thanks.