Perks,
What props are you going to use as the Fletcher kit comes with handed props.
You will need to reverse the rotation of 1 shaft by including 1 extra cog on 1 side only.
A simpler way is to use pulleys on the motor and both shafts.
These can be sized to use neoprene "O" rings to transmit the power.
To reverse 1 shaft fit a slighter larger diameter "O" ring but used in a figure of 8 with the other straight.
Bob