Tom...so as not to confuse.........could I suggest
1. get both new motors mounted down to a temporary bench board
2. mark the motors respectively port & stdb
3. wire the motors with your preferred counter rotating orientation set for FWD movement
4. run the motors for a few hours on a regulated power supply at a nominal 1/4 to 1/3 of the planned final voltage
This will
bed in each set of carbon brushes in the respective motors which now have a preferred rotation direction for FWD movement, however with each motor rotating in opposite directions
As an alternate to this, use the digital tachometer to check shaft speed of both motors in both directions ...if you have an amp meter of sorts, this could be used to better understand the motors performance and efficiency
The data sheet suggests these motors have a 6.35 mm diameter output shaft, however with an equal length output shaft at either end. From this you could consider mounting the motors with the commutator at opposite ends and using the opposite output shafts as the connection for the prop shafts
This will have no effect or impact if you do decide to later install belt drive reductions to the build
Derek