Arms
The most obvious work that needed to be done to the arms was scratchbuilding the curved shoulder and forearm armor parts which really distinguish the Gaz-R/L from the Galbaldy-ß. I wanted to make sure that these were suitably large and stylized so the models would really stand out.

Shoulder Armor
I tackled the shoulder first, since it seemed easier. I first brought a front view of the Galbaldy-ß model into Adobe Illustrator and drew the basic shape of the shoulder armor over it, then printed it to scale with the kit. This drawing included both the large curved armor, and the reshaped base of the shoulder. I pasted the drawings onto sheet plastic with rubber cement, and used these as templates for cutting out the basic shapes I needed.

The base shoulder part is basically the same as the Galbaldy-ß shoulder, with a more rounded shape at the bottom. I glued the plastic profile shape (cut from the template) to the back of the kit shoulder part (I only needed the lower half), which gave me a base for fairing in the rounded shape with putty. I also glued on some thin plastic strips to help me keep the channel around the rectangular upper part and form a base for mounting the big curved armor. Then I glopped on some Bondo polyester putty and sanded the putty to shape. This had to be done to both front and back of one of the shoulders (the other shoulder is the same as the original kit). I later ended up sawing off the outer flared part, since it would be covered up by the new armor part anyway.

I also filled the back of the upper half of each shoulder part with epoxy putty (not pictured). This would make it easier to cast the parts later (since they're not so thin), and provide a larger mating surface for gluing the resin casts together.

The big curved shoulder armor was constructed out of 3 pieces cut from sheet plastic. The front and back were from the templates I printed, and the top piece was just a trapezoid cut to the correct measurements. After gluing these together and verifying that they fit the shoulder, I went crazy building detailed inner surfaces out of layers of plain and pre-scribed sheet plastic, and glued these inside of the armor (the side pieces were glued in at a slight angle, so the top of the sides is thicker than the bottom). These served to add detail and thickness to the armor. It's hard to see in the photos, but there are tons of little plastic rectangles forming an interesting pattern on the upper inside of the part.

I glopped some polyester putty on the top of the new armor part, then sanded it to a curved shape to round out the piece. After a few priming/sanding runs, I had everything looking smooth and uniform. Finally, I scribed a light panel line across the armor near the pointed tip (this is the separation point where the tips will be painted red or blue).

Thanks to careful measurements, the armor fits perfectly over the reshaped kit shoulder part, I wont even need putty when I glue it all together.

Forearm armor
The forearm armor was constructed using completely different techniques than the shoulder. The compound curve made it impossible to just build this part out of sheet plastic. One of the Suku-Suku scratch articles in Dengeki Hobby magazine showed the builder cutting the basic shape for a Zaku leg out of styrofoam, skinning it with epoxy putty, then digging out the foam to form a hollow part. Seemed like a good method...

I used a knife, files, and sandpaper to cut the basic shape for the armor out of a piece of styrofoam (the stiff brittle kind found at craft stores, not the soft packing stuff). Then I mixed up some epoxy putty (eww...brown) and wrapped it around the foam, getting it as smooth as I could (not very smooth, that really was crappy putty). After the putty cured, I sanded and filed it smooth. Note to self: do not buy that cooper/brown colored plumbers putty again! It was hard to mix (I ended up with lots of bits of uncured putty to dig out and fill), hard to smooth when soft, and VERY hard to sand.

Next I dug out the foam. It stuck rather well to the putty, so I ended up melting the last bits of stuck in foam with MEK. The inside surface looked like a Nestle Crunch bar because of the texture of the foam. If I were to do this again I'd use a much denser foam, and probably smooth out the surface with some kind of putty before putting on the epoxy. Lots more sanding and some spot putty took care of this problem. I shaped the round openings at the front and back of the armor part with sandpaper wrapped around appropriately sized cylindrical tools, and glued a plastic peg to the inside so it can plug into the original kits shield mount (I'll probably end up gluing it in place though). The 3 ridges were made from half round styrene rod with the ends rounded with sandpaper, glued on with CA after priming. This part ended up being a lot more work than it had to be, but I learned a lot, and the result looks great. Whew!

Basic shape carved from foam

Epoxy before and after sanding

Below are some photos of the finished shoulder and forearm parts after priming and polishing.