In any questionable area, especially one that could involve enforcement action, it is not always wise to rely on the FSDO for interpretation.
The FSDO level has never had authority to interpret the regulation. Legal interpretation is reserved for the Regional and Chief Legal Counsel offices.
Accepting, listening to, reading, or using an "interpretation" from a FSDO would not only be unwise, but very, very stupid. One has no more authority, and no more defensibility in such an "interpretation," than from anyone on the street.
If you do, at least have the name of the person to whom you spoke, even though that will probably not save you if the interpretation is wrong.
Whether the person at the FSDO is right or wrong is irrelevant. Whether you have it in writing or not is irrelevant. You may get a letter from the FSDO stating that the color red is really black. That letter will not make the color black, however, nor will it serve in your defense if you elect to see red as black.
Having the name of the person to whom you spoke is meaningless. If you're the subject of enforcement action, you can never say "but so-and-so at XXXX FSDO told me it was okay," or produce something in writing from the FSDO, in your defense. The FSDO has no authority to interpret the regulation. Without that authority, anything that the FSDO provides you in writing, or in person, is of no effect.
Some will argue (incorrectly) that an inspector at the FSDO certainly can interpret regulation, because he or she can violate you. This is wrong, of course, as an inspector may initiate enforcement proceedings and recommend enforcement action, but can never interpret the regulation. The FAA Administrator, appointed as an office by an Act of Congress, speaks through his or her Chief Legal Counsel in these matters. Such interpretations are authoritative, and are defensible before an Administrative Law Judge.