I (finally) had some time this morning to continue work on the tail. I'm limited by not having a garage, so I think I'm going to rent a storage unit for a month where I can go at it with a surform and sanding block. I'm expecting copious amounts of polystyrene dust, so I can't really do that outside.
Continued roughing in the shape with a handsaw today:
You can see the cutouts for the taillights, and a couple weeks ago I sunk 4 more carriage bolts in the bottom board, just to make sure that attachment is strong enough.