You can measure the plan sizes in mm and convert to inch stock quite easily, it won't make any difference to the build. Use only the lightest stuff you can find for the fuselage, and it you decide to use thinner wood than specified, remember that you might not be able to achieve the same cross sectional shape, you might run out of wood to sand. There is a lot of wood in the Curare fuselage, and most of it ends up in the scrap bin.
Evan, WB #12.