Originally Posted by Unca_Sam

I'm sorry to say that I've had this very problem, and 'vintage' (1995 and earlier) 26.6mm seatposts seem to max out under 300mm in usable extension. I have a saved search for 26.6 suntour XC posts, which give around 250mm of useful post. Road posts will rarely be longer than 180mm total. I suspect longer posts didn't come about until after wide use of sloping top tubes in frames. I hope you can find what you're looking for, though!