Pulled all the parts and started prepping and deburring each part. Like everyone else here I'm amazed at how much is supposed to happen on this one page with only a couple pictures. I can't remember how many times I had to read and re-read each instruction in order to get the full meaning. Anyway proceeded here to counter sink the tunnel side panels, but everything I tried wasn't very secure, until I attached a 2X2 to the top and then attached the other end to the wall. I cut a slot in one end and a screw on the other and was able to use this for both the left and right panels. It worked well and was very secure while machining the countersinks.
Stabilizing the tunnel panel in prep for countersink
Used hack saw to cut a slot in wood and attached other end to wall stud
