I've built 3 of them and cut the barrels to kelbly specs and took the typical measurements as a double check and they came out perfect with minimal headspace using their protrusion spec. No reason you cant have pre-fits made either.
Always ran smooth BUT when you order one ask for the tactical bolt stop. The standard it ships with broke on all 3 after a few dozen rounds of PRS type use. The tactical is beefy and screwed into the side, it needs to be unscrewed for the bolt to be removed. Honestly not sure why Kelbly doesnt make this standard.
Met Ian at a few matches and hes very friendly and as mentioned willing to go into a lot of detail about their products and their experience to help you out. If I was to use a custom action other than a Tempest it would be an Atlas Tac.