The reason I didn't install an access panel is that I didn't use a fuel pick-up tube, so I decided to mount the fuel level sender directly to the end rib and eliminate a large area of potential leaks. I think this provides as much access as you are likely to need.
The big difference here is the fuel pick-up I am using, which is from an RV-10. The fuel pick-up fitting is a brass hex pipe bushing with an extended tubular screen that projects into the tank. This pick-up is screwed into the flange at the lower rear corner of the end rib. This setup gives you the advantage of a pickup with no movable parts inside the tank (no anti-rotation bracket or safety wire required) as well as a pick-up screen that is removable for cleaning.
My technical counselor (Bob Barrows of Bearhawk fame) was impressed with this setup, and said that is how he has configured his fuel pick-ups. He felt this set-up was significantly better than the standard fuel pick-up tube (and all of its potential problems).