soupA good friend just helped develop the new Phantom Slipper. First split specific hardboot? Not sure but it's basically a TLT5 but a production unharmed up version.
For what it's worth, the Slipper is based on the Atomic Backland. One of the really nice things about this is that the scaffo plastic is fully moldable to different feet.
A number of my splitboarding friends have gone to hardboots. Some are on the Phantom system, and some are using Spark. The canted pucks on systems that don't come canted seem to make a big difference, as well as the boot chosen. Depending on how your Lupos feel, you might not get the flex you want out of them on the down. I know people in Backlands, TLT6 Mountains (and the Speedfit, which is just a new version of that), and one friend who is using the Scarpa TX Pro with the upper buckle and ski/walk mechanism removed.