Model IV Door fitment.

[Wheels]

I ground off the rivets with a dremel tool and a cutoff wheel. (destroying the original windows, but not optional.) After removing the plastic window, I used the dremel and cutoff wheel to shave off the stem as close to the door without damaging the powder coat.
Then I used a punch and drove the rivet body down and into the tubing of the frame. (it will make a nice rattle) Then I cut two oversized holes in the lower corner of the tubing to shake all the bits and pieces out of the door frame.
I put them where they would also drain any moisture that accumulated from my snow operations on skis and such. I may fill the tubes with oil and drain them as an anti corrosion measure, but I don't think that's actually neccesary.

I understand that was common practice at the factory, but I don't know.

Due to the wallowing of some of the rivet holes I am oversizing them to a 5/32 rivet. #20 drill bit. don't ream but do debur. Then you can select the length of rivet you will need based on ALL of your material thickness.
I.E. tubing, lexan,X2? fiberglass trim piece, or replacement, nylon washers, or padded tape etc.
Stay tuned.

[PapuaPilot]

That is exactly what I did during my build (I got the kit secondhand). By drilling a couple of bigger holes at the bottom I was able to shake out the rivet tails. I had the door frames redone with white powder coat (they were originally forest green) and replaced the glass that was scratched and damaged.

I didn't use any oil in mine, but it wouldn't be a bad idea.