Ingenious. Simple, economical and easily modified to suit anyone's situation. Safety is the first concern, but a good harness system should be sufficient. Thanks for taking the time to post it all up. This is the food for thought that may get others interested in posting their "secret formulas" or making modications to suit.
I have been exposd to and am tending to lean toward the significantly more expensive 1.5" x 1.5" x 3/16" angle iron steel with expanded metal deck stands that take two to four men to erect. Then chain and lock in position. Comfortable, semi-permanent, and relatively tamper resistent. At $250.00 plus for each, that is a long way from your ~$25.00 each.
I used to make 2" x 4" wooden ladder stands and posted those plans on-line at
http://www.angelfire.com/on2/LandOwner on the page "Land Owner's Links". I called them "Hell for Stout" Tree Stands. They will resist gravity as well as "growing legs". However, Mother Nature will take her toll on just about anything we put into the woods and their life is about 5 years at the most. Very comfortable though and easy to make.