Thank you, all, for the informative responses... my question has been answered.
The subject of the daisho has fascinated me for several years, whether it is the literal meaning of the word, or the more modern interpretation of a matched set of swords. I suppose daisho - like cars - greatly differed based on the owner's wealth and rank. Those with the money could afford to pay for a matched set, down to the koshirae, hamon etc. Those not so fortunate will make do with any combination that was within their budget. I'm willing to bet that the swords extant today are only a small fraction of what *might* have existed in the past - the rest lost due to fire, theft, wars, recycling or simple neglect.
I was chatting about this subject the other day, and the subject turned to the tsuba on the daisho set, particularly their sizing and the types of shapes that we've seen so far. I have seen sets where the wakizashi tsuba is smaller than the katana tsuba, in many cases very noticeably so, but I have also seen sets where the tsuba are essentially the same size. With the way of wearing the wakizashi across the belly, was the smaller tsuba size adopted out of convenience and comfort? Is that also a compelling reason to go to a hamidashi tsuba? The pictures posted by Eric on the first page were most informative... the first pic shows what appears to be a hamidashi tsuba on the wakizashi, and the other two had the wakizashi pulled out from the obi further than I would expect (maybe to show off the wakizashi in the photo)