World Painter Help!

Heya, I have been working hard on a world painter map recently and have been trying to have smooth snow (better snow) graduating up to smooth up the contours of the mountain, I have tried covering the mountains with 'Frost' on world painter but it just leaves a flat layer of snow on the mountain! I have checked the 'better snow' box while I was exporting the map, also river's etc randomly start falling from the mountains even though I have unticked the 'allow minecraft to populate the world' button! Any help?