Ordered a new seat post for an 80s Fuji Allegro I'm fixing up. Based on several posts on this forum as well as other google searches, I saw that it took a 26.6 diameter post. I even wiped away enough of the grit and rust on the old beat up one that came with it to see 26.6 faintly stamped.

Greased the seat tube, put a little grease on the bottom of post, and the thing barely will go in. Worried about forcing it too much… but is that ok? Any other tips?