Yeah i had the same blindnut issue on my plane. Stupid me sometimes can get impatient so when trying to remove them i noticed they didn't budge. So what i did was bang harder, until SNAP! oops.. the lateral ply wood support ended up breaking. I removed the blind nuts but, now i have an un-ubstructed path. After reinstalling the blindnuts i cut some scrap ply to reinforce the area.
Yeah im kinda hard on my plane. If i dont rip it to shreads in the air, im destorying it on the ground.