A relatively open mouthpiece can help voice the upper palm key notes. Before adding a front F, try substituting the B and G keys for it, adding the F key and side Bb for F#. Work up by releasing the F key and again by adding the side C.
Actually, the front F is pretty uncomfortable on their tenors too, at least according to a friend of mine who plays current Selmer Paris alto and tenor. He built up (or rather, built side) the key with epoxy, making it bigger (but not taller) and much closer to the B key. I think he did it only with his tenor, but maybe the alto too (can't remember).Gordon (NZ) said:Front F tends to work very poorly on many sopranos. For example, it is far more difficult to use Front F on current Selmer Paris soprano models than front F is on their alto or tenor models.