I just noticed that you started with the Cosmos and the Curare. I had a look ant some of the relevant parts, the Cosmos is has much more complex parts. The Curare has only few of them. - like NBD1 NBD2. NBU is a part where it would make sense to mill it to the final shape. But the question for me is: should it be a "pure" Kato kit or a are modifications allowed.

I remember I still have my old OS 40VF - I used it with an OPS tuning pipe - it was really loud, but the power was exceptional - its rather something for the Aurora 45