there are a lot of things to consider in your post.
First of all it might very well possible that one flush does not yield as much stones as the one before. I did 21 flushes so far. After flush 5 or 6 I thought I would be pretty stone free, since I had passed already something around 1.000 stones. However, still 5.000 more stones were sitting in my liver and "waiting" come out. Therefore consider that in the next flush the situation can be quite different.
Secondly Master-Cleanse and ES are very different in their biochemistry. ES will hardly be absorbed by the body whereas Master-Cleanse is famous for its great adsorption. Therefore I personally yould vote against a higher Master-Cleanse dose in order to avoid reaching toxic mg levels in the blood . Magnesium in high doses can indeed be toxic. As a matter of fact somestimes it is used to put pets asleep.
In order to clean your bowels properly after the OO (Olive-Oil) drink I would recommend either drinking a great amount of water (1.5 liter)as quickly as you can. This has a very good cleansing effect on the bowls. Or a salt water flush or activated charcoal AFTER the flush in order to bind all toxins.
However, because of the little experience it might be a good idea repeating the flush protocoll you did and see what happens.