The problem is that the wood shrinks as it dries out, it would be best to make these parts from kiln dried wood to keep shrinkage to a minimum. Sometimes spruce is better, any tight grain soft wood. The other thing to use,not bondo, would be a paintable silicone or acrylic caulk that moves with the wood, good luck.

ok thank you , i was thinking on droping stone on there but ill try it.

Just dig out the old stuff, the refill with paintable latex caulk, wipe smooth with a damp cloth, allow to dry, and paint it. wakazooka