If the station formers are the same size for all lengths of the boat... I would scale in length only.

If the stem chamfer angle is noted In the plans, you will find that the chamfer angle marked on the stems needs to be blunter / a more obtuse angle at the points, for a shorter boat... The solution is to chamfer the stems once they are in place and you can use batons to assess the angle.

If the inner stems are to remain in place the angle will need to have more care taken to fit well. The angle alters from - blunt at the keel - to sharp at the tip of the bow and stern.

Too much information maybe...

Et