The west coast mirrors will fold up if the outer arms are not tightened hard.
If, and only
if, you hit the obstacle in a certain way.
I have bent the cowling on 2 different trucks, because of the way I touched an obstacle and it pulled the mirror assy. (legs and all) with it.
I have been considering some kind of plastic "sheer pin" arrangement for the mirrors. You get to keep the goodness of the west coast setup, you don't have to take them off every time you go offroad but it's the best level of protection if you slide in mud or misjudge a distance and hang the mirrors. Theoretically the plastic bolts would break before a level of load that would bend sheetmetal or mirror arms.
I've thought a lot about this, but it's a "simple in theory, complex in execution" kind of idea.
1. Once you had several samples, the only way to test their effectiveness would be to intentionally crash your truck into trees.
2. They'd have to be soft enough to break, yet strong enough to withstand wind at 60mph.
3. Liability issues: If you do this and mirror comes off on the interstate, that's a whole bunch of liability.