RE: Another Blue Angel build
If it is spongy the dampness of the Minwax might be softening the balsa and causing warping. Not an unusual problem using water base products on balsa. You might be able to super glue a small balsa stick to the dwell area and along with some other scrap balsa build something to hold it out until it dries out. If not you’ll need to fill it with something strong like micro-balloons, but sanding it out could be difficult.