I just recently started mining a bit at your pool, and I do have one question..
I understand the double geometric scoring system, and I love the idea of it...
I am curious, though, why my prop-diff is quite often negative. I'm not starting and stopping the rig, so I'm hashing continuously. Shouldn't I be at 0 or higher? What would cause me to get paid less than my share (proportional) if I'm not 'hopping' or taking breaks in mining?
Enigma
If you've started recently what you're seeing is probably your score building up. Your score starts at 0 and as you continue mining it increases until it reaches an equilibrium (which changes if the pool's total hashrate changes). So at first you'll receive less than proportional, in equilibrium it will be roughly the same, and if you quit at any time your score will gradually decrease to 0 and you will keep receiving rewards for some time.