Ya' know, there are probably as many if not more procedures to break in a new piston as there are choices for pistons. A process I've used in the past on full rebuilds is a series of three hot-cold cycles. What that means is run the engine for about 10 minutes, idle no load, shut it down then let it cool down for for 20 minutes to complete one cycle, then repeat the process again two more times for a total of three times. For the break in process use the same gas/oil mix you ride with. After the hot/cold cycles, I'd run it for about an hour under a light load varying the speed avoiding WOT; no more than 2/3 throttle. Once you've completed the hot/cold cycle and the light one hour ride you should be good to go. Even though the method I describe is one I use for a complete engine rebuild it should also work for breaking in a top end job as well.
One thing to keep in mind is the importance of a good warm up before hammering it. Usually a lap on the track or anywhere from 2 to 3 minutes on the trail to allow the piston to come up to temp should be all you need before you start getting into it. I try to be a little on the conservative side and so far the method I described has done me well. Once you get your bike back together and broke in I'm curious to hear your thoughts on the Wossner piston.