I am a "new" - so maybe moving the old case, but I'm talking about the river. They are far too broad. Practically find the river in Lublin is difficult - on the map is nearly Amazon. Maybe a better solution would be to omit the small streams that do not have strategic importance? (Similar comments had to map Belarus-rivers and watercourses is not seen in practice for the cabin looked like Volga)
Essentially, you are right.
The problem exists within Il2 engine, where it is hard to create the rivers sufficiently narrow,
or as you suggest, to omit some of the waters. Which for to eliminate the width ?
On the other side, rivers are very important landmarks for the pilot, so their total omitting seem undesirable, I think.
Perhaps a pool would solve the problem ?
As for me, it is nothing simpler than to remove the rivers in Mymap_c.tga, assuming the suitable criterion is generally accepted.