I don't think I can make one of these with a shorter seat tube or rear end than what you see here. The tire is literally touching the seat tube with the sliders all the way forward. Of course, one would never run the wheel that far forward as the chain would need to be tensioned.
The 44 MM I.D. heat tube will not only accommodate the tapered steerer fork but it will reduce the headset stack by 15 mm-good for this 5 ' 6 " rider.
The Ahrens design sliders and yoke are a nice feature for me to have access to. The frame as you see it is 3 lb. 14 oz. and is really stout-made to last a long time.