@administrator hello, thank you for the forum, the center plate hole is 60mm. First before anything else, take time to go through the entire document part by part analysing how everything is assembling up, because the document has a lot of missing data in general and wrong data. A good example is hub bearings, wrong bearing codes, then some dimensions are missing on one part, but u can get them from another part in a different page of the document just by relating the parts.

Before I started I took time to read and understand the document and ordered all my hardwares way before I started, which is huge, since you need to know how things assemble, how thick the parts are when assembled for you to be able to know the bolt length (dash number).

That said and done there is an easier way, find on internet another different document of same project, Google "furia metrics", this document is more hectic to work with but once you get time to sturdy the initial document you can get some missing data from the furia metrics document.

Eg the 60mm dimension I got it from this other document, it's a critical dimension because that what gives the hub ability to be semi articulated.(blade flapping)

The central gearbox assembly is not shown anywhere in the documents, because everything about it is identical to the tail rotor gearbox in terms of assembly and operation, even though somethings like bearing covers are different sizes but same bearings, and mode of lubrication.