Ok found best solution for me:
Launch Mount&Blade.
In the first Menu' , press "configure" and go in tab "Advanced" and put flag on "Enable Edit Mode (Be warned ...etc)"
Exit, choose your mod or native mode and press Play Mount&Blade
Start new game ... when game is ready and you enter in the main map (it's not important the point where you are in the map), you can see in the lower left side of the screen the "Terrain" button.
Press it :
enable "place river" (if you want a river in the map sometime ... if you have an nvidia card remember that could be a problem with river texture that you can solve
in nvidia panel ... if you have problem tell me)
polygon size : 5 meters
Lower to minimun : Vegetation, Rugedness,Valley and Hill Height
Increase to maximun : Size y & Size x
Well , now press "Copy" Button and exit game.
Open a NOTEPAD.TXT AND PASTE THE STRING : you will see sometihing like 0x00003....etc.
Well done ... now go in directory Mount&Blade/module/ where you have other directory like "native" and also other if you have some mod installed.
If you want to change battlefield size on "native" , open native directory and search file "scenes.txt" . Open it : only the first lines are important
for our goal and are these :
.
.
.
scenesfile version 1
412
scn_random_scene random_scene 1792 none none 0.000000 0.000000 240.000000 240.000000 -0.500000 0x300028000003e8fa0000034e00004b34000059be
0
0
0
scn_conversation_scene conversation_scene 0 encounter_spot bo_encounter_spot -40.000000 -40.000000 40.000000 40.000000 -100.000000 0
0
0
0
scn_random_scene_steppe random_scene_steppe 1792 none none 0.000000 0.000000 240.000000 240.000000 -0.500000 0x0000000229602800000691a400003efe00004b34000059be
0
0
outer_terrain_steppe
scn_random_scene_plain random_scene_plain 1792 none none 0.000000 0.000000 240.000000 240.000000 -0.500000 0x0000000229602800000691a400003efe00004b34000059be
0
0
outer_terrain_plain
scn_random_scene_snow random_scene_snow 1792 none none 0.000000 0.000000 240.000000 240.000000 -0.500000 0x0000000229602800000691a400003efe00004b34000059be
0
0
outer_terrain_snow
scn_random_scene_desert random_scene_desert 1792 none none 0.000000 0.000000 240.000000 240.000000 -0.500000 0x0000000229602800000691a400003efe00004b34000059be
0
0
.
.
.
If your file is like mine ... you can see that at the end of many lines there is a string similar to the one the you pasted in the notepad ...
i 'm talking about the "0x0000000229602800000691a400003efe00004b34000059be" ... keep attention that there is also a 0x300028000003e8fa0000034e00004b34000059be.. in the first line that is different and shorter.
You have to replace only the "0x0000000229602800000691a400003efe00004b34000059be" with the string that you took before and you have reach your goal.
When you renter tha game, The battlefiled size will be 3 or 4 times higher than before ... i use a chronograph , with regular version , only 30 second with horse to pass from one side to the other of the battlefield...with this version
120 seconds....
) .
If you have a mod ... keep attention that if you see that there is a directory called Module System in the main directory of your mod, you have to
change the scenes.txt file but also enter this directory "Module System" and search for Module_Scenes.py file.
Open it with text editor and replace the same strings done for scenes.txt.
Your goal is achieved also for the mod. No need to have python program or something similar
If you have some problem , post here. Sorry for my english, i'm italian
))