I can make two suggestions. Make sure the -C flag is optimal for your card. I get best performance using -C 1. You could try -i 0 but this might make desktop lag unbearable, it depends on the power of your card.
Thanks for that, the -i 0 made the difference. GPU load is now constantly at 99% and not between 85% and 98%. -C 2 is still the best value for my card.

Undervolting to 925 mV is stable for me. Further undervolting got the cudaminer to stop mining.
I'm mining now with constant 66°C at 53% fan speed