So my son has an M-7 and the tunnel is pretty much trashed. He has spent a lot of time over the past two years trying to polish the tunnel with no success. So I am looking for any help or suggestions on a good process to paint the tunnel. Thinking of going semi-gloss or flat black but am not sure regular primer and paint will work. Any help or suggestions would be great. Also not looking to spend a ton of money powder coating. Thanks