this diff retarget system a bit fail atm
and someone playing with it "nicely"

coming in with 50-100MHs => getting 10-15 block in 1 min, and leaving
coming back 30 min later => after gettin his 1st block, average will be like 0 cos there where 30 min pause between 2 block => gettin his 10-15 block => leaving
and starting again.. and again

wanna hug this guy xD