I've seen quite a few of the bolstered and non bolstered H&H rifles and in my opinion the only one they look right on are 375's.The H&H rifles don't need them and like Huvius,I've never seen a cracked action although I have seen some blown up barrels.
I wouldn't build a sidelock rifle now with bolsters on it as I prefer the the non bolstered look and unless the action body is really light,they are unnecessary.