I agree with Fil, the "slow" recipe is the good one. I tried it many time myself - so far it produced biggest stones. I was taking a glass of olive oil and a glass of lemon juice over 2-3 hours in small portions with 15-20 min breaks, starting at 7pm. Also I used hot water bottle to warm up the area from right lower ribs to the spine. Another trick I used was biting on hot chilli pepper in between potions. It is said to increase liver's heat. Warming up helps to melt stones on soften them before they could be expelled.
You don't have to suffer, go easy on your next flush!