I am think the only option is going to be 2 seatposts - one for tall people and a sawn off one for shorter people.
i had thought about milling a groove but it would be in the minimum insertion region of the seatpost when i would be using it, and as i would have it at the maximum height it probably would not be safe
it probably makes sense to have the inline post sawn off for short people as it will also help shorten the effective top tube by having the saddle further forwards
I am think the only option is going to be 2 seatposts - one for tall people and a sawn off one for shorter people.
i had thought about milling a groove but it would be in the minimum insertion region of the seatpost when i would be using it, and as i would have it at the maximum height it probably would not be safe
it probably makes sense to have the inline post sawn off for short people as it will also help shorten the effective top tube by having the saddle further forwards
what spare saddle do you have?