I've been riding a Specialized Toupe Saddle on a Campy Record seatpost for a year with one problem. Then, last week, my Toupe saddle slipped nose up during a ride. After four repairs roadside tightening as hard as I could turn with my allen wrench, it kept slipping nose up.
I took to the LBS and they said the Record seatpost has had proble with slippage and he showed my how the teeth on the clamp was worn and seemed to not be able to grip the seat rails.
So I switched to the Bontrager XXX Light Seatpost. 10 miles into my first ride I heard a little tick and the nose of the seat slipped up slightly. The saddle stayed in place for the remaining 50 miles but the slight angle upward bugged the hell out of me.
On my last two rides this week I leveled the seat and tightened but always get a slight shift of the nose upward during the ride. The saddle doesn't move around just a slight shift nose up from level. No matter how tight I get the clamp it still happens.
Get a seatpost that has the notches in the right place. You are setting it up where it is comfortable and when you ride it slips into the first set of notches. You are basically tightening it with the notches not indexed to each other. You may not be able to find such a post. There are seatposts that use two (sometimes four) screws/bolts to adjust the angle and that is what you need. Roger