Rate my mining performance

[Duane Vick]

I am using an ASUS HD7790 DirectCU II OC 2GB card on GUIMINER-Scrypt. Ran the card overnight from 10:30pm to 7:00am. I was getting 246khash and using middlecoin.com's pool which mines the most profitable coin at any given time. 95 shares accepted, 10 stale/invalid (seems high to me).

Thread-concurrency 8000
vectors 1
gpu threads 1
worksize 256
intensity 18
gpu-engine 860
gpu-memclock 1500

Any suggested tweaks? How is my stale rate? Stales seem high this run but on longer runs it is usually half to 1/3rd this amount.