How permanent is this structure going to be?
At the very least I would get a posthole digger and start asking questions on carpentry websites.
Looping chains around shallowly buried objects won't help your case much.
You might be able to get away with 1 ft of depth if you have the base secured to long, horizontal beams that are wider than 6 ft (if they are buried, then this width shouldn't be a problem, right?)
Your ramp support is inadequate. You'll want runners under the planks and you will want to connect the supports to each other.
There is a thread around here about a guy who was building a drop in... he used Google Sketch-up to model his plans.
Read on another forum: "If someone held a gun to my head and said, "You have to move to Salida tomorrow", I'd probably do it. If they told me I had to go to Breckenridge instead, I think I'd just let them pull the trigger."