in the lighter stuff you can hold the plate when heeling the boat to windward, this stops u falling out and the plate rocking. also, mine doesnt ten to rock in the heavier stuff so im guessing yours is the same
no problem, in medium/heavy winds i haven't really taken note if its rocking mainly because there is more important things to focus on but i will look out next time.
maybe also a new friction pad, this stops the plate popping up when beating so may provide a bit of extra stiffness - http://www.lasersailing.com/shop/uks/product/2