Here's another notion about the fin count/sequence.
We know from the At the Creation book that Harley was having problems getting good cylinder castings in the 1907-08 period. They sent Frank Ollerman to Standard Foundry in Racine to "iron" out problems.
So, I wonder if the 17 to 14 fin switch was made to somehow aid in the casting process which had been giving trouble. That an early style cylinder was used a little later in sequence does not seem unusual.