Sewing the codpiece to the front of the cummerbund was the old way of doing things and one we are trying to encourage people to move away from. As we have learned more and more about this costume over the years, we've found that the codpiece is a big piece of fabric that is sewn to the front of the vest. The cummerbund just holds the pouches, it is not connected to the vest or the codpiece.
You can have a one piece bund and cod or a two piece; both are acceptable for Lancer as long as the proper look is achieved. The problem we have had in the past is that folks were making their bunds way too big (more of a tube top than a cummerbund) and their codpieces way too small. Here are some photos to give you some ideas: