The other thing that happens in creating WDS frames is companies lengthen the headtube, which also shortens the top tube length. In reality, perhaps a bit better, simply because it leaves the seat tube in a better position.

Although you can always add a longer stem to a bike to give you more room in the cockpit; it at at times can seriously affect the handling of the bike as well. Of course, it's different from one person to the next, but I would seriously THINK about this and talk with the PROS before doing too much of this. Ideally, the bike should fit you as well as it can BEFORE you start making changes to it... in that regard perhaps another brand would fit better and even better yet Luna could definitely make that happen.