Bruder CAT Excavator Replacement Linkage

This is a replacement linkage for the Bruder CAT Mini Excavator (02456). OPENSCAD model created by prompting Gemini Pro 3.1 like so (and then performing minor parameter updates):

I want to create a replacement part for a Bruder CAT excavator model as a OPENSCAD model. At the end of the excavator arm is this H shaped linkage that connects the hydraulics with the bucket.

It kinda make sense to describe the 3 layers the part is made of when viewed from the side of the excavator. We'll use a coordinate frame the has X point along the main long axis of the part, Y up and Z depth. The layers are stacked along Z.

The origin frame is in the middle of the part.

First layer:

Shaped like a capsule/rectangle with round ends. length along X 35mm. Height Y 12mm. Flat part, thickness in Z 2mm. Along positive x there is a hole in the center of the rounded end with a diameter of 5mm. On the other end at the same place is a peg pointing inwards with diameter 4mm and depth 4mm. We should make the part "bone shaped" in that it can should be tapered towards the middle, reaching a height of only ~ 7mm in the middle.

Second layer:

Connects layer 1 and 3 via a round connection (i.e. a cylinder). Diameter is 3.5mm. The z depth is 18mm. I need a part of constant 3.5mm diameter of 7mm length around the middle, but apart from that the diameter can extend for more stability.

Third layer:

Same as 1st layer, but the hole has a diameter of 4mm. And the peg has diameter 5mm.

To double check: Total depth is 22mm.

Best printed laying flat with supports and using PETG with lots of walls.