Just got back from White River in AR and the universal consent among the rental boat docks is to use aluminum props on the rivers. Their reasoning is the aluminums might bend/break easier but they are cheaper to replace and repair. More importantly they claim the aluminum prop won't transfer as much of the impact to the lower unit on the Merc motors, which is almost always a $300 repair. The prop with my motor is OK but fairly frayed around the edges. I'm thinking of keeping as a back up and getting a new one. Do others agree here agree that aluminum makes more sense if you're constantly navigating rocky rivers with gravel bottoms and varying water levels? If so, what brands are reasonable and can you get them cupped?