Once a games starts ?

[K K Rossokolski]

As far as im aware you both must specify which rules to play by then both are stuck with the same rules.IE if you pick extreme assualt and variable visibilty and your opponent agrees then thats it.Someone correct me if im wrong.

Not quite......Only one player...the player setting up the game,...needs to make the selection. One would expect both players to agree on the options..as they have had to in the past...but this is not a MUST situation. Once the game is started, no changes to the options can be made.