Chris,
it seems you figured out most of the terrain.data format. Did you document it somewhere ? I'm currently trying to write an import of a HF2 file from L3DT. The difference with a bitmap is that in the HF2 file I have all x,y coordinates with float data of their height in meters.
My biggest challenge is to convert those real life meters into a scale for DOS. I also am trying to find out why your bitmap needed to be width and height +1, I presume it has something to do with the data format of the .data file. So that's why I would love to see some documentation somewhere on it
