Currently the keybinding style assignation is bugged.
When you change the keybinding special style in the game client, it doesn't save the style into the "ManiaLayoutSelected" property. When starting the game, it defaults to Normal Style for most keycounts, except for 8K, 10K and 18K where it defaults to Left Special Style (18K and 10K only default to Left Special style if you have SplitStages disabled in skin settings, that way they use different keybinding assignations compared to 18KSplit and 10KSplit). The only way to play with other settings is changing them manually every time you start the game (the game doesn't load the keybindings when starting the game if you set "ManiaLayoutSelected" to 1 or 2 by manually changing the configuration file).
Also, there is no option for playing with special style with 1K-3K-5K-7K-9K anymore (the option doesn't appear in the keybinding wizard). I don't know if that was intended or is a bug. Because of that, you can't use 2 keys for the central key.