Fixed positions never work for long, period,,,ya need to stay mobile to suit changing senrio's. If your in the middle of nowhere,,,, maybe they'd work out,,but there's better options avalible IMO.
I'm not so paranoid at this point to even consider such a thing. Hell,, I could have bought a missile silo ( a old SAC base) a few years back w 10 acres, all equipped for 45K,, if I was that worried!! Now that was a real bunker,,,not some piece of pipe stuck in the dirt. It had several "real " blast doors that no one would ever get through in a million years plus it was just a small under ground city with all the utilitys done!!
If I was that paranoid that little tin door would do little to comfort me,,, you could pop that thing with a small "porta- power" if you wanted to,,, real easy. How to hell would you defend it the way it's set up? Amonia/bleach mix at the vent and your toast!!!! No Thanks, I'm all good with my hidden cave in the middle of the woods that's half way up a cliff with several exits. It was free too, just cost a bit of work. Just one of the bug out spots I have. Not that I'll ever worry about that to much!! I'm not that tweaked!! It's just stocked with minimal survival stuff, in 2 PVC tubes with everything needed, simple and not over the top,, paranoid.
I'm more worried about environmental emergency's/disasters than anything else, screw all the the "dooms day" shit!! That's what I prep for.
Dooms day,, is just that, why let it rule your life being scared and wasting money that's better spent on your family in other ways? Wilderness/survival training is a better choice and common sense stocking up is best IMO. You don't need a major base ops to survive if the SHTF for real. If it does you'd better have that old SAC base to truly survive.
That pipe thing won't do shit for ya for long unless your really out in east bumb- fuck somewhere where it will never be found. Just an infa-red , or magnatomitter ,fly over would bust ya.