Never thought about the rivets potentially causing spider cracks. I do like rivets because they are cleaner. I've done both ways and cant really say that one is way better then the other. On the rub rail I used rigid with the ss concave insert (ss4510). You will have to use a heat gun to bend around the corners and a rubber mallet on the ss insert. Your boat is going to be a little tricky with the ss insert but it sure will look nice when it's all finished. If the ss insert does not work out the you could always glue a piece of rope in there
http://tacomarine.com/ccp51/media/im...e/V21-9613.pdf
strick