RE: hinge removal
If you are very careful and very lucky, you can sometimes cut them out.
Cut the hinges first to remove the surface. Then use an X-acto to cut on either side of the hinge and slice it away from the balsa. Now try to pull the hinge out. Then you can cut the slot to the required width.
It's really best to rehinge at a different location but if you really have to, sometimes this works.
Dave