For 7790(260x) managed to obtain the best values in the config: -h 256-a 4.
Here's what happened:
09:42:03:659 bc8 GPU 4: HashCnt = 256, time = 1102 ms, hashrate = 232 h/s
09:42:03:674 580 GPU 3: HashCnt = 256, time = 1101 ms, hashrate = 232 h/s
09:42:03:694 bc8 Round
09:42:03:704 7ec GPU 2: HashCnt = 256, time = 1121 ms, hashrate = 228 h/s
09:42:03:709 580 Round
09:42:03:719 d10 GPU 1: HashCnt = 256, time = 1122 ms, hashrate = 228 h/s
09:42:03:744 d10 Round
09:42:03:754 730 GPU 0: HashCnt = 256, time = 1117 ms, hashrate = 229 h/s
09:42:03:764 730 Round
09:42:04:769 bcc GPU 4: HashCnt = 256, time = 1075 ms, hashrate = 238 h/s
09:42:04:779 bcc Round
09:42:04:804 d54 GPU 3: HashCnt = 256, time = 1079 ms, hashrate = 237 h/s
09:42:04:809 d54 Round
09:42:04:814 c90 GPU 2: HashCnt = 256, time = 1074 ms, hashrate = 238 h/s
09:42:04:824 c90 Round
09:42:04:839 398 GPU 1: HashCnt = 256, time = 1077 ms, hashrate = 237 h/s
09:42:04:849 398 Round
09:42:04:854 aa4 GPU 0: HashCnt = 256, time = 1074 ms, hashrate = 238 h/s
09:42:04:864 aa4 Round
09:42:05:869 bc8 GPU 4: HashCnt = 256, time = 1072 ms, hashrate = 238 h/s
09:42:05:894 bc8 Round
09:42:05:909 580 GPU 3: HashCnt = 256, time = 1079 ms, hashrate = 237 h/s
09:42:05:919 7ec GPU 2: HashCnt = 256, time = 1075 ms, hashrate = 238 h/s