How far should I stick it in?

[Saddle bum]

Engineering problem:

Road bike, Audax Aluminium frame + Ali seat-pin.

How many diameters minimum in the frame for safe and secure operation, taking into account the number of diameters sticking out?

Opinions?

[snotrag]

At least 100mm odd, and the seatpin should extend well below the tt/st join.

Most posts will have a minimum insertion mark on anyway...?

[Mandog]

2 in the pink, 1 in the stink!