[ryans69chevy]

I took my outer skin off. It's still off now I guess. It was time consuming to do, but I got it off nicely and fixed it up pretty good.
If it was me I would take it off as if you were planning on reusing it. Even though you stated in earlier posts you are going to buy a repop. Just in case the new roof doesn't fit exactly like you want - which is a common issue with repop items.
How I removed mine was by first sanding all the paint off around the whole roof where you have #2 on your drawing. You wouldn't go down the back of cab beyond the roof seam I guess. Then you will see or feel a bunch of spot welds. Take punch and punch the center. Drill them out with spot weld drill bit. There will be a ton of them! Then I cut directly in the back seam across the whole cab above the back window. I then took a flat screwdriver and dug under #2 in your drawing and started prying little by little until it popped off.
To answer your other question #5 isn't butt welded. The drip rail is spot welded. From your picture the spot welds are all about under the "R" where in your picture you wrote "drip rail". I also removed them to clean up those areas and put them back on.
Take a look at my build thread if you want to see some pics. I might even have some more that I didn't post if you want to see more of what I am talking about.