A possible improvement to the process would soften the edges of the bump maps. On the bump map layers (high bump map and low bump map), add layer mask (mountain mask channel) and blur the mask by about 25 pixels. This will smooth the edges of the bump maps so the mountains don't suddenly 'spring out of the plain'.

It will also kill a couple of the smaller bumps/hills near the mountains, which may or may not be desirable. I'm not sure if this is better or not, consequently.

K.