The usual advice is to stake trees at a low level, but these birch trees on a site we are working on are so tall and spindly that the whole trunk flexes in the wind. The contractors have attempted to lash a pole to the stem but this has snapped (but the stem is OK). Would it be problematic to stake the tree higher? I was thinking something like the bottom image (with flexible straps holding the tree) but with higher stakes e.g. 1.8m.