I would never recommend attaching any homemade stand to a tree. Any homemade stand needs to be free standing to be safe. Trees have a very large wind profile when leaved and move a lot. Even very large trees. This puts stress on any fasteners connecting the stand to the tree.
I've been guilty of leaving treestands out too long. While I've checked them before the season to make sure they were sound, I found that after a couple years, trees grew around them enough that they could not be removed. I don't use these stands, but they do create a safety hazard. One never knows when some kid trespasses and climbs into one. I'm in the process of slowly removing old stands using a ladder.
I'm getting to the age where I've stopped using climbing and hang-on stands (my favorite). I'm now using ladder stands and free standing box stands. I started building these so I could take young kids out and mentor them. I now see that they will likely be my future stands as I age. I'm now refining the designs for my own use. Here is my latest 6x6 design and build:
http://www.habitat-talk.com/index.php?threads/foodplot-stand-transfered-from-the-qdma-forum.5529/
I'm slowly working on reducing cost with each subsequent build. I've got the cost down to a little over $500. Considering a good solid comfortable ladder stand runs over $300 and these will last my lifetime, I think they are a better long-term bet.
I do several things to try to keep "surprises" out of my stand and I've had a few. On some of my early stands I had window openings that did not close. Not only did this make it easier for game to see motion in the blind, it left the blind open to critters. One problem I had was with buzzards:
http://www.habitat-talk.com/index.php?threads/buzzard-mischief-transferred-from-qdma-forum.5818/ Another was raccoons.
I now use push-out type window closures. This creates shade at the opening adding better concealment and allows the windows to be closed during the off season.
I was surprised this spring after entering a blind in the dark and realizing I was not the only one in the blind. It turned out to be a family of mice. It just of easily could have been a squirrel. I now keep a small container of rat poison in each blind. Any rodent entering the blind finds it and doesn't survive long enough to take up residence.
The final issue is insects, specifically wasps. I solved that problem by spraying the inside of the blind with a permethrin product. This is the stuff not approved for use on the skin but is great for spraying coveralls during spring gobbler to prevent ticks. All insects hate it. It bonds with material and is good on clothing for several weeks during turkey season unless I get caught in a downpour or wash the coveralls. I find one good spraying in the spring and fall is sufficient. This is the same stuff I use on my seedlings I grow at home so it is readily available.
Thanks,
Jack