Flexing of Captain's Seatpost

[LCI_Brian]

I'm setting up a mountain bike tandem with a child stoker kit (for bike paths and dirt roads). The captain's seatpost has about 8 inches of post showing, with 4.5 inches inside the frame. That's about 0.5 inches above the minimum insertion line. With the long stoker stem extension, putting pressure on the stoker handlebars causes the captain's seatpost to flex. But with a child stoker, is that really an issue in practice? Also, should I consider getting a longer captain's seatpost?

[zonatandem]

Our suggestion: longer capt. seatpost . . . or a larger framed tandem in the future.
Don't think a child stoker would cause/abet flexing of your seatpost unless this one heck of a big/powerful child!
The only effect a child could have, if child is *aggressively* attempting to steer the rear of the tandem and you interpret that as flex.