Is ther a Way to setup that every Time the active windows have the size of 75:25?
If you simply want to have 75:25 panels ratio at MC start, then one of the ways is to create user defined command and pass it as command line param to MC executable.
1. Go to menu Configuration > User defined commands
2. Add new command and name it e.g. "set panels"
3. Change
Command type to "Internal commands",
Module to "Multicommander (base)",
Command to "75 / 25"
4. Save changes.
5. Create shortcut to MC and add command line parameter '-AutoRun="set panels"' (command name must be enclosed in double quotation marks)
If you want a panel to be automatically resized to 75 after activation, then it's probably not possible.
P.S. Some time ago I've got an idea of "events" like OnTabCreate, OnLeaveTab etc. So each event would allow to execute user command. But then I realized that most likely it would cause much pain with almost no gain for Mathias to implement this.