On My touring bike to use My traditional Campagnolo 2 bolt seatpost,
which was to be at its Max height, I had another seat post [plain top Kalloy]
machined to match ID's in the overlap, and welded onto the older Campag Post ..
then, of course, weld machined down to the same OD.
I cut off the extra when it hit the Bottle boss in the front of the seat tube.