Hi, We also engineered and fabricated our own still and columns www.seattledistilling.com . From my heavy reading through the TTB manual...you are allowed a 60 day window to have your equipment together (in relevance to what you put on your application) from when you submit your application. Otherwise you will need to go back (after your DSP approval) to amend and add any other unlisted equipment. I agree with Brian, that you must have your knowledge in order in terms of welding/brazing, etc. Safety is obviously a concern, but also wasted efficiency and profit if you develop vapor leaks - and there will be leaks. Let me know if you have any questions! Cheers...Ishan.