Hm. OK, well as I said in the original post, this would be temporary. I do not want to source new cones, etc, etc, and a larger diameter axle, just swap out the hollow axle for a solid one. It seem fair to assume that since most tandems (at least that I've looked at...) come with a solid rear axle there is at least some strength advantage to it. I don't really understand the claim that a solid axle is smaller than a hollow one- isn't 10x1 the same, whether it's solid or hollow? Or am I missing something here?