Two stroke break in, synthetic oil OK?

yeah just go for it, never had a problem.

I heard its best to use non-synthetic oil for break in so that everything can wear quicker and therefore seat better with better compression.

I have always used a synthetic if possible on all my motors.

I would say it's best to try to stick with the same oil as much as possible.

I've never switched to non-synthetic after top end rebuilds and have never had a probelm. I run synthetic all the time; break in and later. Never had an issue. I also don't buy into the 'take it easy', on a new top end ideology. Heavy load on the motor creates more cylinder pressure which drives heavier ring contact resulting in a more thorough break-in and ring seal. After I do a top end, I run it hard right off the bat; real hard. I've never had an issue with this method and have done it for years; in my bikes and cars. Break it in the way your going to ride it; hard. Worthy of noting; there are those that adamantly disagree with this method so do what you feel comfortable with.