Having lost the 6-way ISP cable that I use with the Dragon, I ordered some connectors so that I can make up a couple of replacements. As I have plenty of 10-way cables, I thought I'd try one of those by only using the first six pins on the sockets. As expected, it worked perfectly.
BTW, those connectors are difficult to find. Digi-Key and Mouser are out of stock, but RS has plenty - the stock number is 673-7694.