Re: 1993 Merlin
At the time we usually used either ritchey, syncros or ringlé posts that are not known to be undersized.
One of mine has a kingsberry, the other a syncros. On the 15inch the posts feel tight but the 13inch is fine.
Could be with the thicker tube on the 15 and up, the 13 uses 31.8 der and the others 34.9, the tube is a one piece machined compared to a lot of other brands that use two pieces welded together.