The singleSelect config in RowSelectionModel already behaves as a property (in the sense that it can be changed on the fly to control the functionality of the SM), it's just not documented that way. If it's not desired for this config to be a writable property, then a setSingle(true/false) function would be an alternative. The point to all this is that it should be possible to change the single/multi selection of the grid on the fly (which it currently is, just undocumented).