Shoot boys,
Back in the day all we had were homemade climbers, you step up onto what you would call the foot piece and strap your feet to it, get a big 'ol bear hug on the tree and up you go! No hand climber, just your arms.
I carried a 4" wide strip of 3/4 plwood about 20" long to lay across the upper brace of the climber to sit on. Yes sireee boys, them was the good 'ol days!