In addition to the AN bolt, I've seen washers like this used to spread the load over a larger area and keep the tube from collapsing. It also seems to me that it would be beneficial to have a solid section of shaft where the u joint is bolted (with some sort of plug inserted into the column). Not sure if this would be overkill or not.
https://www.pegasusautoracing.com/pr...oduct=3077-003