Spotter RGB matrix Left and Right at the same time

Hi,

Built in spotter option can display both carleft carright at the same time. How do I achieve the same with custom animation?

Currently I have custom animation for [SpotterCarLeft] and [SpotterCarRight], I can display both at the same time after unchecking Clear background when active. But this also means it wont clear Gears,Flags etc. 

[SpotterCarLeftRight] does not exist. (null)

So how do I get it to clear everything else apart from each other? 

Also anyone knows how the Content stacking: Left to Right should work?