Perhaps a SM420 specialist like
Novac could answer your questions about the yoke with a longer spline engagement. I recall from a machine design course nearly fifty years ago that a self-centering spline should have an engagemrnt length of at least twice the spline diameter, but I cannot verify that.
53moneypit also had some good comments last year on driveshafts and spline engagement
driveshafts and spline engagement.
Hoyt
