RE: lag bolt steps
Head to your nearest Family Center or feed store and buy the grade 8 bolts with a eye on the end. Then drill a 5/8th hole in the ends of the boards on the outside half and put in a 2 inch steel peg. Then screw the bolts into the tree. 2 per step. When you have em in the tree, put your board on and pegs down through the bolt. Snap in your pins to make sure the pegs cant lift and you are done. Its a sturdy setup and rather cheap. The bolts are about $2.09 a pound around here. Ok, so its not all that cheap but its solid and removable.
Stryker777