I have been considering installing a posi for maintaining 'dually' footing on slippery concrete boat ramps.

I have lost traction while pulling my buddy's boat out of the ocean with the camper on, at low tide. The issue went away with 4X4 engaged, but NOT being able to move forward with the ocean coming in behind you is not a nice feeling.

What posi would be best, and what will hold up to all the weight? I am guessing an air locker ? Experience/advise ? Should I bother?

The truck is empty during winter, and at maximum weight capacity in the spring, summer, and fall with the camper and boat.