Actually, they are embedded about 30-inches deep, because at 3-feet deep we're starting to get into the ground water table and digging deeper than that with a post hole digger is TOUGH. We're also in hurricane country, but that doesn't stop us from hunting and we don't want to find it tipped over, particularly with us in it.
Also, I don't need plywood siding here. For the most part, in these Florida "Tropics", we get some chilly weather that will suck the heat out of the body pretty good over a four to six hour hunt. Certainly not like the cold you guys in snow and ice country suffer, but cold to us none-the-less. AND, there are over 300-days of tee shirt hunting weather here.
So, my siding is hunting camo. Camo strips are CHEAP, light weight, conceals the hunter, easy to construct (staple gun), easy to replace, can be impregnated with permethrin for killing bugs, and doesn't hinder the passing of the wind.