Hi Michael,

Correct me please if I am wrong...doing this by script is clever but manually (for now) it might be best done like this...

1. Countersink head part; we just use concentric / 'lofted' circles representing the back of the countersunk part to create:

male solid 1 ( with clearance )
for the 'plug head seat'(!!!)
E.g. top-down: 1st circle 12mm dia 2nd dia circle 8.5mm, spaced apart ~4.5mm becomes the male "cone" shape...

Solid 2
The main shaft as I indicated in my preferred macro approach can just be 8.5mm diameter 'rod/cylinder' or what later becomes a pass thru hole at 8.5mm x 100mm length.

We then join 1 and 2 together so the cone and the rod become a united clearance shape...Then bolean into the "block"...and the male solid does its job...

!!!
In this particular example please note this plastic plug simply passes
through and is seated in a piece of solid aluminium (say 20mm depth). It sits inside the aluminium fairly snugly, then what protrudes (about 80mm) goes into a wall.

The screw head will sit flush with the front surface face of the aluminium.

I hope its that simple.

If I could have a video of these functions in context it would really help get me making this object to an almost perfect and realistic drawing....

I will post the results here ;0)

Stefano