For the Claymore Miner v 12.4 using 4 Sapphire RX470 Nitro 4GB, I am using this bat: 

ZECMiner64.exe -zpool ssl://zec.supernova.cc:2242 -zwal username.worker -zpsw password -i 7

Im only getting about .15 zcash every 25-26 hours

What can I do to improve performance?  Miner speeds read 276 - 288, Driver date 3-16-17 version 21.19.525.258.