Bondo works great for repairing arcade machines. For damage to the
bottom edges your better off replacing the plywood. Bondo sticks
really well but I've had it break off and that sucks after you've
finished a nice paint job. Use a router with a spiral or dado bit to
cut off the bottom 6-8 inches and then replace it with new plywood.
Screw and glue in the new plywood and fill the crack with bondo. Go
easy on the bondo because it's hard to sand and gums up sandpaper real
quick. A good tip for sanding bondo is to spread a light coat of
mineral spirits over it (I use my hand but I'd suggest a rag) and then
sand immediately with a ROS. The bondo still gums up the paper but
it's more of a slurry than a thick chuck. It makes better use of the
sand paper and gives you a smoother finish. The paper will will also
separate from its backing at some point as the mineral spirits eats
through it quickly. Go lighter on the mineral spirits and accept that
you'll need a lot of paper if you put a lot of bondo on there.