[Help] Importing heightmap for surrounding terrain.

[B2P1]

I'm having problems importing a heightmap to the bf2editor as explained in this topic:
https://www.realitymod.com/forum/f189-modding-tutorials/99405-creating-heightsmaps-geocontrol-bf2hmt.html

I created a 256 level and resized the Gray-scale image to 771 pxs, but when importing I keep getting the error that it's not the same size as expected.

Also how do I create a 4km map that still has the highest terrain detail possible in the playable area?

Edit: I fixed it now I'm having troubles with bf2_tpaint...