I have to disagree to an extent, the purpose of a crossover relief is to protect the hydraulic circuit pressure spikes mainly but can also protect the mechanical parts too.
While it's true that the side of the plow with the collapsed cylinder won't benefit from the crossover valve I've found its usually the extended side that takes the brunt as it catches easier since it's angles forward, the side of the plow angled back usually deflects off an object much easier and doesn't need the protection.
A trip mechanism is important but usually won't help with high loads on the outer most wings as much, that's where the crossover relief comes in.
A lock valve could be used to protect the hydraulics also but cost about the same and doesn't offer any mechanical protection.
This is my experience, and there is a reason most plow manufactures incorporate a crossover relief into their plows.
