Z axis...

It looks like I have four options here...

1 - Drive the Quill direct from the bolt point where the depth gauge mounts at the front.
2 - Drive the manual lever shaft on the right side
3 - Drive the power-feed clutch shaft on the left side
4 - Drive the knee lift

Points -
Option 1 seems to be the most common but adds a lot of bulk to the front of the head and costs a little Z axis travel.

Options 2 & 3 are similar, both will suffer from the rack backlash but option 3 is the neatest one, backlash can be reduced with the clock-spring.

Option 4 is a contender I think, it gives a massive 300mm Z travel, but suffers from stickiness and has backlash in the bevel gears. The force is reasonable - I measured my one and if my figures are correct, it needs approx 1Nm to lift the knee based on the handle length of 160mm and 6kg force on that handle 6kg / (1000/160) = 0.96Nm

The backlash is a factor but the Z is usually used to plunge or position - both of these are done in the positive direction so maybe backlash does not matter here?

Thoughts?