Looking at where my avionics were going to install and planning to use the top of the tunnel. I quickly realized I need an access plate, since getting in from the top would be a lot of work removing all the stuff I'll have installed up there. A lot of guys install an access panel on their planes and I should have made one when I was building this a long time ago. But oh well. It was actually really easy.
Cut a hole, add screw holes, dimple, install nut plates.
Make cover plate, install,....done