Steve,
I saw your thread several days ago but didn't have time to investigate my parts. I am using a fixed pitch prop also. I have ordered an MT but have yet to receive it. My prop extension is the "deluxe" unit that Van's sells; made by Sabre. See photos. The plate fits on the prop extension very precisely. I am not familiar with the Sensenich prop and extension. Maybe it?s different?
I need to know where you are installing the comm and transponder antennas. Are you placing either of them aft of the spar? If so, which one and about where? I was thinking of putting the transponder antenna forward and the comm antenna aft of the spar. That way it won't be shadowed by the gear legs. I'm head scratching and could benefit from some hints from other 4 builders.
Sincerely,