Unfortunately a part of article 2.3.1 about the length of a hoof has been left out when publishing the new edition of FIPO. The correct text is:
The angle of the hoof must be in line with the pastern. The hoof length must be natural and not exceed 9.5 cm. Exceptions to the 9.5 cm rule can be made when a written proof (e.g. from a breeding show or a veterinarian) is shown that the horse has a stick measurement of 145.0 cm or more, in which case a length up to 10.0 cm is allowed.
Any artificial lengthening is forbidden.
A revised version of FIPO 2010 and the page in question are available for download from the FEIF website.