Alright, here you go!
Tools/Materials:
Dremel/Rotary tool
Cutoff discs -
http://www.dremel.com/en-us/Accessories/Pages/SubCategories.aspx?catid=58&catname=Cut-Off+WheelsCylindrical Cutter bit -
http://www.dremel.com/en-us/Accessories/Pages/ProductDetail.aspx?pid=194Toothbrush or any soft bristle brush
Sharpie
Xacto knife
Straight blade paint scraper
Cardboard, about 5"x5"
~200 grit sandpaper or a Scotch Brite scuff pad
00 or 000 steel wool
Pop a cart into the case and mark where you need to cut (or just use my pic as reference). See the little Sharpie mark? That's where you need to cut back to in order for GBC/GB games to fit.
Now slide that piece of cardboard in between the ploy cover and the case itself (as if you were installing a custom cover). This will keep you from cutting the clear sleeve, which would pretty much ruin your day.
Time to make a mess. Hold the Dremel vertically as in the pic with the cutter bit. Start cutting away at the wall above the DS slot where the GBA games are held.
Keep hacking away at it slowly, being mindful that you don't push down past the bottom of the case.
Hoorah!
Now you need to do the same on the DS cart holder side.
After cutting down the majority of the extruded portion, switch over to the cutoff wheel and take out the piece of the base that's in the way.
Grab the paint scraper and carefully cut any jagged edges or burrs that are left.
Now use the scraper to cut down any of the "walls" that are left. You may also need the Xacto at this point to trim any little pieces that are still hanging on.
You've probably got a pretty big mess of plastic shards in the case at this point, so take a minute to wipe it out with the toothbrush or whatever you like (canned air, paper towel, etc.)
The case should look pretty close to this now.
Now use that sandpaper/scuff pad to clean up the surfaces wherever necessary. Don't be shy here, really cut away at whatever little chunks and whatnot are left. The case should now look like this.
Last step is to go over it with the steel wool to clean up the last bits of crap. There are other things you can do to make it look even closer to the original texture, but it's just a waste of time IMO. In normal light, you can't see any remaining scuff marks at this point. The only reason you can see them so well in my pic is because there's a 55W halogen aimed directly at it.
This is in nothing but daylight. Can't see any remaining scuffs or marks
Now pack up your game, give it a cover, and admire your work!
