FC, have a look at how the leaves are created in Vue, it's actually the 2 last branching levels with the leaves attached to the very last branching level that create the branches in Vue trees. And this is an alpha plane. So with Xfrog, you will need to cut out any trunk and lower branching level just to keep this structure, then export from Xfrog (lwo is best), import this object in Vue and render using the top camera. Uncheck cast & receive shadows, indirect lighting, and you don't want any specular highlights either, all this will be created later when this render will be used for leaves. Render and save the colour picture, along with the alpha picture. Then use this render for your new tree leaves.