Peter- First thing I thought of was that the shop used what ever fit at the time of initial set up. Some one who has a good feel for how seat posts fit seat tubes might lend more understanding if they could examine the bike. Like can you see any distortion in the seat tube around the back side of the seat lug? If you run your finger down the seat tube do you feel any high/low points or bulges. Look down it with a flash light. Does the insides look the same from the top of the lug to as far as you can make out or is there a difference in how the insides of the tube look, along it's length. How does the 27.0 post slide into the seat tube. Smoothly, no rocking, the same along the post's full length? You say the shop measured the post. The original Campy posts did have their size stamped on them. But there real size could drift from the claimed, even along the same post. Did the shop measure the frame and if so how? (not that it would be the "real" size any way). If the frame was cooked during the build the area around the lug can distort 0.2mm easily. How narrow is the binder slot? Is the slot the same width along it's length? Do the faces of the binder bolt lug ears have lots of wear/distortion? Have you tried other posts? What are their sizes? How well does a 27.0 post hold with normal tightening?
So many more questions before I'd say what was the best approach.
> ------------------------------
>
> Message: 9
> Date: Fri, 16 Oct 2009 16:35:07 -0700
> From: Peter Adler <adlerpe@mac.com>
> Subject: [CR] 1971 Raleigh International: Oddball seatpost size?
> To: <classicrendezvous@bikelist.org>
> Message-ID: <a06240800c6feaebf145b@[192.168.0.3]>
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> Hi, all; first-time poster...
>
> I'm currently building up what I believe to be a 1971 Raleigh
> International frame. I got it as a rattlecan job: Chromed
> forkblades/stays and Nervex Pro lugs; missing/overpainted decals;
> badge removed (but rivet-holes in the right locations on the
> headtube); serial number F5332, which is a 1971 frame according to
> Sheldon's site.
>
> My intention is to build it up as a loaded tourer: Mafac Racers,
> Sachs/Huret Duopar, Suntour barcons. But in the build process, I've
> run into a weirdness: My LBS measured out the seatpost size as 27.0,
> when all documentation I've ever seen on Internationals (and Reynolds
> 531 frames generally) says 27.2. I've been researching other frames
> that used Nervex Pro lugs, just on the possibility that the frame may
> have been misidentified; but all signs point to Raleigh, except for
> the seatpost size.
>
> My suspicion is that someone clamped a 27.0 post in at one point, and
> crimped the top of the seat tube. If that's the case, wouldn't I run
> the risk of further damage (and saddle slipping) if I use a seatpost
> that's really too small for the seat tube? Obviously, I have a lot
> more inexpensive seatpost options (both period and modern;
> single-bolt SR and Thomson are my preferences) if it's 27.2, but I
> don't want to fix something if it isn't busted.
>
> I see three possibilities:
>
> 1) 27.2 seat tube clamped to 27.0 - get the clamp expanded to the
> normal size (by what method? Is this an LBS thing, or can I do it
> myself?)
>
> 2) 27.0 seat tube - ream it out to 27.2 (definitely an LBS thing)
>
> 3) 27.0 seat tube - get a 27.0 seat post and get over myself
>
> Any thoughts? Has anyone else encountered an International with a
> narrower-than-normal seatpost?
>
> I'll get some photos together and post some links. Thank you!
> --
> Peter Adler
> Berkeley, California
>
Andrew R Stewart
Rochester, NY