Thanks! Machining from pieces is part of the original design. The advantages listed are the ability to use smaller milling machines, reduction of complicated machining setups and less skill required.
The fasteners shown on the pilot beam are 4-40s. I have been getting them online from Albany County Fasteners. These are stainless steel and are called trim hex head. I don't think that they have any 5-40s though as they jump up to 6-32 after the 4-40.