I picked up a Guid stem at the SD Velodrome Swapmeet on Sunday to potentially replace the Ambrosio stem that came with my "new" PX-10. My calipers confirmed that the Ambrosio stem is around .1 - .2 mm thicker diameter than the French Guid stem, so that probably accounts at least somewhat for the difficulty in getting the Ambrosio removed.

So I'm planning to switch to the Guid stem, but there's no minimum insertion line on it. I know it's probably from an era when no one would bother with a min insertion line because it was expected that only a little bit of quill would be showing, but I prefer to ride with my bars around saddle height, so it's important to know how high I can set this stem. Does anyone know or have a guideline for this sort of situation?

Thanks!