The site uses shares submitted, which isn't really a reflection of your "hashrate" reported by your miner - it is what your miner calls work units. On my own Gridseeds, I've noticed that if I use higher difficulty I see a big variance in my shares submitted per 10 minutes. I use 128 for my 6MH and 10MH rigs of Gridseeds. For less than 16 of the 5-chip Gridseeds, I would use 64 for your difficulty.
I have 20 GS grids each as one worker with your pool. Is there a place I can see shares submitted then instead of hash rate if it's not the most useful of number? If I increase my difficulty you're saying I'll see a hashrate closer reflecting what I see locally, but it sounds like that doesn't really matter, more of an appearance issue?
I've noticed that if I have my seeds clocked higher than 850, they look like they are running awesome on my end (no HW or anything), but the rate reported by the pool is always 2-3 Mh/s lower than what I'm seeing.
My assumption is that they actually aren't actually running that great, even at 855 I see this problem. So I put them back to 850 and now what I'm seeing on my end, and what I'm seeing at the pool are just about the same (minor variance but nothing worth sweating over).
+1 i leave mine at 850 - very little variance, and completely stable at that frequency....