We have a little update from Kuoppa Gomez Bikes
for you. Martti posted a photo of their Soulrider
frame. This one has a 19.5" toptube. If you take a closer look you find rear brake mounts and drillings for optional cable mounts. Furthermore it looks like there is an integrated seatclamp and pretty strong dropouts. We asked Martti for more details. Since they accept custom order this TT length is probably not the only option.