Are you using the Alexis fork or the spmod fork? Alexis has a bit higher hash rate than spmod. Otherwise, I don't bother changing clocks, but zer0k uses those 1080's so maybe he has some insight.
i read alexis - 1.0 on the pool
http://zpool.ca/?address=16yLHLoeyuCLPMXkVpC3gyrRYvwRGwjKJrSummary--------Miners------Shares.......Hashrate*------Reject*
skein.................4-----------8.2346%----9.4 GH/s-------0.2%
Details Extra Algo Diff ES** Hashrate* Reject*
ccminer/alexis-1.0 four1080TI,c=BTC,skein,stats skein 0.8 2.4 GH/s
ccminer/alexis-1.0 one1080TI,c=BTC,skein,stats skein 0.8 1.2 GH/s
ccminer/alexis-1.0 three1080TI,c=BTC,skein,stats skein 0.8 3.2 GH/s
ccminer/alexis-1.0 two1080TI,c=BTC,skein,stats skein 0.8 2.6 GH/s
I have:
9x 1080 ti
1x 1080
3x 1070
I feel I should be about 10.5gh and I am 9.4-9.7gh
I am going to boost power to 75% on all the 1080 ti's