On a Dazzler I've got, I made the entire bottom of the fuse removeable so I could move the battery anywhere. As it is, the battery is ALL the way back. I would go the removeable route. Hate to have to cut the glue when something with the battery needs to be done.

Maybe:

1. cut hatch out
2. recover hatch piece to get edges of wood sealed
3. insert 2 (1 on each opposite side) small pieces of lite ply into the hole and glue flat to bottom of fuse (inside fuse) so that 1/2 of each piece over-hangs the hole.
3. insert hatch, drill 1/16" holes through hatch and lite ply. Unless CA has really dried well - carefull on pushing with the drill bit.
4. insert screws

Shouldn't take more than 15-20 minutes, a little lite ply, and some CA

-s