I sure wouldn't go that high. Stack them that high without anything on them and see how stable they are. They have a very narrow base for something that high. Figure all if would take is for someone walking by you camper and bumping may start toppling one set and then the others are going to go and the camper is going down or maybe some high winds. Or on some soft ground that you didn't know was that soft and have on side sink. I wouldn't do it. Maybe 2 or 3 high maybe but not higher. Also if this is for unloading then you are not going to get it as close to the ground as before for storage.
This is IMO for what it is worth.