I try it and it's a bit crazy. :-) I try to set -1, which is 10 meters and one lighthouse was rooted deep into pier, but on second nothing change (look at the far one):
But i must thank you, because you push me to right way. I edited Lighthouse.dat and that's it! I will tune it a bit more, but i think some value between -0.01 and -0.03 can be good for all slopes of terrain.
