@Gordon Nichols, I have one of the clamps you suggest but I can't see how it would help here. At the rack end, you can see the set screw with a nylock lock nut.
I thought about drilling straight through as you suggest but thought maybe the rack shaft would be hard to drill. Also, I would be making the rack shaft weaker. The cross-section is already reduced by the flat side.
At the steering column shaft end, the set screw goes into a groove in the splined bit. So, it just keeps the shaft from going in and out of the tube.
I have a super beetle steering shaft with a u-joint on each end. I might be able to shorten it.
Or, maybe I could just trust that the set screw won't shear.