Middlecoin diff too high?

I just found about Middlecoin and wanted to try mining them for a short while to see how profitable it would be compared to straight LTC, as I've been mining.

I mine on a 4 x 7950 rig, as well as my alienware laptop with dual 6990m's. (I know, and understand the risks)

Middlecoin seems to use 512 as the minimum difficulty, whereas once I connect, I often see difficulties in the 130-150 range. What I'm wondering is, is everyone in the pool missing submitting valid shares to the network because the pool is telling them the static 512 diff even if it's actually lower?

Maybe I mis-understand how the whole deal works, but I'm just used to difficulties that are much higher, maybe the difficulty I'm seeing is inaccurate?

Also I notice that most of the time, my laptop is just sitting there doing nothing. Proportionally, it should be the same as the rig or anything else mining the network, but the 512 diff seems to cause the laptop to perform poorly.

Thoughts?

(P.S. I would post to the right middlecoin thread, but I'm a noob apparently)