The thing that takes so much time is shutting off boiler letting the system cool a bit then replacing spent bark. Then reheating. And waiting another 2.5hrs for around 100ml or more. From 2.5kg you can expect 150g oil being 90g safrolesomething from the ones in my friends neck of the woods. Need I remind 2.5kg of dried bark is a fuck load of digging!?
Very simple and cheap setup but takes forever... Imagine taking a pressure cooker and attaching a pressure relief valve on the steam port of say 30-50-psi or better if your pressure cooker can safely ahndle more. And attach copper tubing from there to an inverted lid of another one. Supported from below with a couple bars running form two lab stands across form each other. Now take 2.5kg of bark (don't pack it too full it wil need a lil expansion room) and tie it up in chese cloth or steel screen or some other avail cloth (or a close fit collander with a silicone bead around the lip to make a tight fit). Then palce net in lid and atach top (act.bottom of pot) The top naturally bottom of pot needs to ahve a hole drilled in it with a flanged copper fitting through the inside and soldered to a piece of copper tubing on the outside then coiled under a sink faucet of into an ice bucket then into a small carboy with an overflow and a bottom drain.
Here are some pics of a small 2L lab scale steam still.
http://www.heartmagic.com/EssentialStillRunning.jpg (http://www.heartmagic.com/EssentialStillRunning.jpg)
http://www.heartmagic.com/NewReceiverHOW.jpg (http://www.heartmagic.com/NewReceiverHOW.jpg)