After wa-ay too many ears of limbo I came back to this. Remember Goram Ram and his ergonomic handle?
Finally I made the handles for my Jackie. Interesting. Even without the wrist straps it feels better, having eliminated the necessity to push with the thumbs. Now I'm waiting for the sealer to dry to put the handles on and start working on the leather wrist strap. Man, I had to re-drill the holes for a larger diameter of screws, as longer screws are thicker. It was a scary moment, but seems like it worked.