The main thing to be aware of regarding 2 strokes is that they rely on very limited lubrication compared to a 4 stroke. On the 503 it would almost certainly be 50:1 fuel/oil premix, the 582's normally have oil injection with a separate tank. In practice the one thing you don't want to be doing is shutting the throttle completely for any length of time. This means no long descents without either maintaining some power, or regularly bringing it back to cruise setting for short periods. The oil injection system is not quite so critical as it is delivered as a function of both engine speed and throttle opening, so will still have some being supplied with a closed throttle. Don't go thrashing them from cold either! I have manged nearly 1200 hrs without problems in my 447 powered flexwing - so they aren't as bad as many people make out....