Doing it gradually is the best approach. I built up to 2.5 after a few months of just messing around. It never really gave me a headache that I can recall, but I don't get headaches very often either.
I think the best approach for me is to keep this one on the shelf of "novel but not to be done". It will live between my ability to cross one eye at a time at the cost of spotty vision and migraines an hour later, and flexing my back just right to pop a rib out of place which looks amusing but hurts for days