Seatpost length

[VeloVT]

How close can you be to the minimum insertion line and still be safe? Is this line "conservative" or is it really at the edge of the post's tolerance?

Lots of seatposts come in 100mm size gradations (e.g., 250, 350, etc). If I put a 250 mm post in my frame, I will be about 1-2 cm (roughly) from exposing the min insertion mark (though it will not be exposed). Is this safe, or kinda borderline not safe (assuming a carbon post which is likely more fragile than an alloy post)?

Wish they made them in more lengths... I suppose if I had the tools I could buy a longer length and cut it down to something in between...