Hi William,
Arron what is the best way to resize the map use the design or the heightmap.
Both have their uses. If you want to down-size the heightfield, or if you want to slightly resize the heightfield (e.g. 1024x1024 to 1025x1025), then the resize heightfield option is better.
If instead you want to drastically up-size he heightfield, then re-sizing the design map and re-generating the heightfield is "better". Resizing the heightfield is a simple linear interpolation, which means that it doesn't give you any more detail. Conversely, resizing the design map and re-generating the heightfield does give you more detail, as L3DT will use additional fractal inflation, erosion, etc to make the high-res heightfield.
Another option is to use fractal inflation directly to increase the size of the heightfield. To do this, select the 'Operations->Heightfield->Fractal inflation' menu item. This will double the heightfield size using a fractal mid-point displacement algorithm, which adds a bit of detail. It's also rather fast.
Maybe recommend a better method, but rather work in same size maps from 2048 to 4096 and resize them to larger maps, will it automatically fill dead areas or will this have manually done?
Very tricky I fear. Most of L3DT's algorithms aren't written to "fill in" areas (fractal inflation is, coincidentally, but most others aren't), and I think there'd be a major rewrite required to make this happen. I'll thinker about it.
Cheerio,
Aaron.