I built a Jacob Kuntz rifle using documentation form two in the MET, generously provided by Tom Curran and Eric Von Aschwege (sp?) The forearm on the rifle is rounded just forward of the lock, rather elliptical being deeper than wide. The stock is rounded right up to a knife edge at the barrel channel. As you move forward toward the entry pipe, the forearm becomes more "V" shaped, but still has rounded sides. The upper forearm is very "V" shaped, but there is about 1/8" of wood thickness at the apex of the transition into the rounded part to the barrel channel. Be careful not to make the forearm too thin prior to shaping the "V".
On other Lehigh rifles I've had the privilege to study, the lower forearm is quite rounded.