Maybe put the probe on a spring loaded linear sensor, and move down until it hits a target offset (could just be read by a simple flag in an optical sensor)-- resulting in hitting a constant target force.

This is amazing! Limitation breeds creativity indeed

How does this only have a single star.

This is genuinely mind blowing.

Wow that's nuts. What a great idea! I wonder how much of this the commercial flying probe machines can do already. Pretty cool to be able to have this on a home scale.