coomarlin,
I wouldn't attach the battery to the hatch, this just serves to put additional stress on the hatch, and its securing. I went along the lines of geoharry , but made the hatch removable for future use. I just used the balsa that I cut out as the cover, and glued a retaining frame on the inside of the fus. If you glue the hatch back on, its a certainty that you will require access in the near future