It got bad enough for me that I quit kava for 8 months once.
For stone:
1) I need to strain very well, until all the fibers are out. I'm talking like straining it 5+ times through nakamal@home's strainers. That is the biggest factor.
2) Empty stomach. I don't eat after 3pm before an 8pm drinking session. Liquids are ok (water, juice, not coffee or other caffeinated beverage), the less caffeine in my system the more I enjoy the heady feeling. (nothing to do with the stomach)
3) 3 cups water is fine, I like that ratio too
4) Don't move around too much, stop walking around the house, no dancing, don't lie down, just sit down.
5) wait 45mins to an hour after the drinking session to eat a light snack, I like something with bread, too me it feels like it soaks up whatever stone is left in my stomach so I can sleep.
6) It's possible the batch of stone you got has more of the nausea kavalactones?
if during the session the stomach issue comes up, drink some water, eat a few saltines and watch some tv. It sometimes passes in 15mins. I occasionally have to use an antacid like tums.
when I was new to kava, it was the worst (lasted up to 2 days), but as time went on all the discomforts went away... looking back I really should of just started drinking one or two shells a night for a month to get my body use to it.
, ofcourse I danced haha.)