Study the pictures of the cases as there's a fair bit to learn from that. And to be honest you don't need to cut as much as he's done to get the results.

Matching transfer between cases and cylinder is a good idea. As is grinding all sharp edges and casting flashing. Grind a radius on all edges, corners and what have you. Fluid likes radii, not sharp edges.

Don't knife edge port entries. Transfer flow is subsonic so nothing gained.

Do match up the RC valve. Lots to be gained here.

Don't polish anything to a mirror finish.