I have the opposite problem with servers that use "medium" or "low" scenes.
It has an easy solution:
1. Go to (i.e. your using this route for your install) C:\Lock On\Bazar\Terrain\Scenes
2. If you want use always i.e. "Low" scenes, copy the file "low.scn" and paste on other directory i.e. "LOWBACKUP". Rename it as "High.scn".
3. Backup your original "High.scn" file from C:\Lock On\Bazar\Terrain\Scenes
4. Paste the file from inside "LOWBACKUP", now named "High.scn" and overwrite your "original" High.scn file.
You can do the same with "Medium.scn" file. Always remember to backup the files.
Now, whatever scene settings the server had, you always will use the ones you want. The key is knowing what scene type you want to use. If you often change the scenes settings, depending of the mission, maybe this tip is useless, because invalidates your election, but if you want play always in one or two settings only, its a good choice.
As an example, I have the three files made from the "High.scn", so I always play "High" :-) (I cant fly w/o trees. I love trees and forest in LOMAC)
S!