before starting the mission you have "parameters" on the right hand top side of your screen, click on it and you'll get to the Options menu to chose all your options.

But you have to do all over again because next tme you reload the mission, because those parameters are the default ones, you'll have to set your parameters again.

To avoid this simply use notepad to modify the default options to suit your needs.

I did this to avoid taking 5 minutes to change everything back everytime.

good luck !