"In your face space coyote"-HJS
+1 on the screws.
I cant think of a screw type I havent snapped.
Use plenty, dont overtighten them and they should be fine.
A stud/wire/cable checker is a very good idea- drilling and hoping is never a good plan, especially not on friday at 5pm.
Oldgringo is correct some of the new deck screws will hold the plywood to the studs better than many other types of lag screws. Keep in mind that the studs are probably only nailed to the top and bottom plate with two or three nails each. That may be your weak point of attachment. Try to get the plywood to the top and screw into the top plate.
You might consider a way to jam in a ridge pole between your two plywood plates. The ridge pole will be up high so it will not be in the way and will reduce the chances of failure.
Hi; i'm another one with a background of carpentry and cabinetry. You'll be fine with three studs. I would use a 2x2 and glue and screw. Use PL 400 as the glue and it will never separate from the 1" ply. Also don't use drywall screws, use decking screws. You'll be fine. I have one eye bolt into a stud at each end of my BB and its fine . People think too much and worry too much about structural stress etc. Its only your body weight. To give you an example , one nail nailed in a board at 45 degrees can hold 200#. You've got 18? screws altogether on your 1" boards. I think you'll be fine but like someone else said make sure you hit the studs well.
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