Is a Hirth coupling extension possible?

I have a bicycle crankset where the two halves are joined with a Hirth coupling in the middle of the spindle.

The problem is it was made for a bike where the shell width was 61mm, and the standard for all road bikes is 68mm I'd love to use it, but would need to extend the width by that 7mm difference.

From an engineering standpoint does it seem even remotely possible that an extension piece could be made? The spindle has a 30mm diameter, and the tooth profIle is between 3-4mm deep at the outer edge.

Would the fact that the tooth profIle is more than half the required thickness make the construction too narrow to hold together? Or would it not matter when all bolted up tight?