No pun intended, but this is old news. 😉
Multiple such projects have been discussed before in DPReview forums, and the DIY forum really doesn’t provide any better mechanism for giving details of such projects or browsing them — a well-indexed DIY user article mechanism would make more sense than a DIY forum. DIY instructions are either omitted or posted at other sites — as I’ve been doing for years, mostly in the Sony NEX forum. For example, here are two 2012 Instructables, both introduced in the NEX forum, explaining how I made a mount for my NEX-5 to be used as a digital back on an old 4×5 ( http://www.instructables.com/id/Large-Format-Adapter-For-Your-Mirrorless-Camera/ ) and how to make custom lensboards including one that can take SLR lenses ( http://www.instructables.com/id/Custom-Lensboards-For-A-Large-Format-Camera/ ).
Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work.