very interesting ideas. Often carb shafts are not a straight shot from a linkage or shafts a offset on twin carb set ups.
Me being a tight ass, I make my own cv joints. Its called a short length of re-enforced fuel line that slips over the shaft with screw clamps.
Just use a piece each end of the shaft.
Simple principle just grab some hose and twist it, when one end turns the other end turns the same amount, and short lengths can deliver quite a bit of torque.
Gordon you can even dress it with stainless hose braid,