Like others have said, I'd recommend increasing dietary choline before attempting to supplement any particular dose. That failing, try purchasing an inexpensive bitartrate if you just want to relieve the headaches. Experiment with doses (starting on the low end) you can administer with a small, portable measuring spoon for easy use when you need it. Too much of the bitartrate can cause diarrhea, so just get to the point at which it seems to relieve your side effects. The less choline you have to take, the better.
Unless you're already noticing significant effects now, I'd try raising your dose of piracetam, if you find the choline to be working. As far as I've read, current studies suggest that 4.5g to 5g split into multiple doses will yield the most benefit.
