I made plywood centers for R2's feet. I decided to use some scrap plywood and 1x2s. I started skinning one outer foot and it is moving along nicely! I've been using contact cement to adhere the styrene to the wood and it's working well. I'm holding off finishing the outside until I get the drive motors mounted.
I got a cheap caster for the center foot online for $4.00, with free shipping! Amazing!
I also got a 12V 7Ah battery with a charger. Now I just have to pick a few brains online on how to configure the electronics.
I may take the feet to work to continue the build on my lunch breaks. Hopefully by next weekend the feet will be finished and I can start on the battery boxes.