Hi,
My apologies for this inconvenince indeed the paramter is documented although it doesn't exist in the API.
It will be fixed in the future release.
As for limiting the number of UI controllers, you can set it via iisu Advanced Configuration tool:
1. Launch iisu Advanced Configuration tool
2. Click on Advance mode button
3. Change the value of a field called "Max controllers number"
4. And save
the setting will be saved in .xml file which will be loaded at iisu startup and the controllers number will be limited according to your setting.
Hope it helps.
Zofia