Gobsmacked by your skills, Lukasz. What a superb rendition of the aluminium doped finish - and everything else!
Looking forward to seeing the end product.
Just one point though: are you happy about the belt chute and drum?
When I was building my CSM17 I opted to leave the left panel off to display the internals. (wish I'd added the cross rigging, when I see yours!) After much looking at refs etc I surmised that the empty belt comes out of the left side of the gun down the chute to the drum, while the empty casings eject downwards from the body of the gun - see attached youtube of gun firing.
https://www.youtube.com/watch?v=ApmMbiF0nVsThus, I altered chute and drum feed to meet each other, inside the left upper longeron as in attached picture. (Sorry about quality)
I may be totally wrong and welcome anybody else's view on this, but I thought I'd mention it before you mount top wing and add rigging etc in case you agree!
Great story and I can't wait to see final result
Sandy