Over the past few nights I've been working on the aluminum skirt piece, which is what attaches to the bottom of R2-D2's body.
There are different materials to chose from with the skirt. There's a fiberglass version available which just needs to be mounted, a styrene (plastic) one and the aluminum one. Mine is an older version made by JAG and just needs to have the slab pieces attached. Newer versions already have the cut outs on the skirt for the pieces to attach to, so no need to measure and mark where to place them.
After marking off where each slab will go in pencil, its time to use a center punch and punch where the holes are to be drilled. This prevents the drill bit from wandering while drilling. The slabs aren't very wide compared to the 10-24 thread screw.
I opted to attach the skirt to the bottom frame ring plus the frame rods.
Now that the holes are drilled out, its time to place the slabs where they will be mounted permanently. With the holes drilled and the skirt elevated by the frame rods, its just a matter of marking the position of the holes with a Sharpee.
Then I used the center punch to make sure the drill bit stays put.
Now I was planning to only drill part way and tap the hole, making sure to not drill thru the other side. However, with my tap and die kit, the hole wasn't deep enough to get more than 2 turns, not enough threads to secure it in place. On my first R2's skirt, I used various epoxies and the slabs eventually popped off. Since I drill and bolted them into place, never an issue. That said, I decided to drill all the way thru and tap the entire hole.
Each hole was drilled out with a 5/32 drill bit, which allows for a 10-24 tap to make the threads nicely. To secure them in place I am using a 3/8" inch 10-24 thread screws and a split-lock washer.
To smooth out all those little holes for painting, I am using JB Weld, which when dry, sands nicely.
To keep the JB Weld from sliding around while wet, I'm using some painters tape rolled up to keep it in place. Then, its just a matter of sanding smooth, touching up as needed and a few coats of satin white paint.