Have more than half of the parts listed, and the search continues for the rest of them. I havent bought the instructions yet, but when it comes to the 4215b Reddish Brown x93, the alternative is 1x4 Bricks, which looking at the prices are obviously a point in the alternative directions. The 4215b's, are they primarily on the outside or inside? Also, I just finished Lachlans Hoonicorn, would buwizzs work as a replacement for the batteries?