#1 - There is no scientifically valid reason for not using synthetic oil during break-in. This is an old wives tale that has been perpetuated over the years by people who have a vested interest in non-syn lubricants. I'm sure everyone remembers the BS put out by Harley and their dealers about how synthetic was too slippery, would cause roller and ball bearings to skid rather than roll, etc., etc. I still remember the original ads for Mobil 1 where a person couldn't keep a screwdriver soaked in Mobil 1 from slipping through their fingers, which supposedly proved it was "slipperier" than plain old oil. Whoop-de-doo! I can use that method to prove that cooking oil is slippery also, but I don't think I'm going to put in in my engine.
#2 - I have always used a break-in method similar to Maverick's. The first 50 miles, warm the engine up thoroughly before riding and then ride gently - you don't want sudden large changes in temperature. The next 450 miles, ride more normally but still avoid WOT at maximum rpms. Without lugging, accelerate fairly hard for a short distance to load the rings against the cylinder, then coast down to stabilize the temp, then repeat. This will rapidly seat the rings.