Richard Sachs at one point wrote the target was an 11 cm stem. That is not very specific as it leaves out handlebar shape which can vary quite a bit, some bar shapes have more forward “throw’.
Falcons were known to have long top tubes, 22.5” ctc or more would not surprise me.
Ernie Clements had definite views on things.
to get a best idea, align the saddle to the crank position, not just by measure of the saddles (unless the same make / model) , with an assistant compare at 9 o’clock crank position a plumb bob dropped from you knee with a line that passes by the pedal, when those are the same, it will allow you to know you are matched. Then measure pelvis to bar center and to hand position with you “on the hoods”.
in general though, an 11- 11.5 cm stem seems to yield comfortable control of the steering. Not all can achieve this and still have a good position.
you might also compare the trail numbers of the two bikes. A chance that the falcon has less trail, even with a more relaxed steering angle on the Falcon.