Back to the model first stage.
First I assembled the inter-stage section
Then I started with the body of the stage. I marked small bumps for have a reference where to put the positioning ring inside.
I assembled the parts using the bulkheads, and the fit was good.
The two segments joined.
The interior side of engine’s compartment was clad.
… and finally the stowage compartment of the parachute.
Now I’m dealing with the engines (51), and I not found a solution that I like.
To be continue.