I looked at this briefly a while back, and so my memory may be a bit in error. But I am sure others will jump in.
If memory serves. The auxiliary drives were retro fitted. Even though it sounds like Kathleen is fitted with two props, I have seen several examples with only one prop that emerged through the hull to one side of the keel. The ones I saw were on the port side. Maybe just coincidence that I only saw single props on the port side.
I think a retro fit of one of the Robbe units would be easy. You don't need a lot of power, as it really is just an little extra push.
My only thought at the time was changing to a brass prop for scale appearances.
I looked at the Robbe units, but they did seem a bit expensive, but considering they can include motor, gearbox, shaft, and prop, perhaps not that expensive.
My thoughts at the time were to have aux drive to push her nose through a tack in light or difficult winds, as I used to sail in a pond surrounded by high rise flats, and the wind could change in a few meters. The other thought was to bring the boat slowly home if the winds died completely.
