Hi Stuart, I manufacture timber decking materials. 35mm is possible of course, but not the best choice for most species because most sawmills still work to imperial measures even though they mostly can talk these days in metric. For example, the sawn size closest to 35mm is 38mm, this is the old 1.5″ size. If you start with 38mm sawn, you cannot get 35mm clean from the timber after drying. You would have to start with 50mm timber and that would be a huge waste of wood and an expensive way to do this. From 50mm (depending on the species you might get 43-45mm. From 38mm, you would get about 30-33mm.