This one goes on the left (I think) Pitch + Roll
.
and this goes on the right Pitch + -Roll
.
If their inverted just switch them, but if your pitch is right but your roll is wrong then just change one of them by removing the - and put the - on the other hinge

simply add a plus (+) between them, no spaces (this acts like an or logic gate, i.e. it gives an output if at least one input is given)
e.g. Pitch+Roll (the order doesn't matter)
if one of the rotators movement is inverted, simply add a minus (-) which will invert the output
e.g. -Pitch+Roll or Pitch+-Roll etc.
i'm no FT wizard but this is very basic math so i can still understand it