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...just as a heads up about something else to be aware of: Sometimes, people buy or find a nice seat post that is just a little too large for the frame. They want to use it anyway, and they force it in. You can force it in, but not without a little bit of deformation to the seat tube (which you can usually spot as a bulge line on the outside). Those guys are much more difficult to extract, after they've been mounted for a while.

Hopefully, that is not your circumstance. If not, the heating/cooling along with ATF/acetone (both from the top of the post and the bottom, if you can do so) will eventually yield results and ought to preserve the post as well. I presume those posts are anodized, not painted.