Tu or vous?

[Chancer]

This is for a letter that I am writing to someone who is now a friend and who I have tutoyered for a few years, however the letter will be a formal one adressed to her in her position of the president of our diving club, I was going to start it "Madame la Presidente", so I guess that is the first question is, is this the correct formal way to address her in writing?

Its a fairly serious letter, a bit of a shot across the bows requesting her to follow an administrative procedure laid down by our governing federation to accept and validate my existing diving qualifications, something "the club" although not her personally, has steadfastly refused to do for a couple of years before now. I say her, in fact it is the club that I want to abide by their responsibilities but there is a chance that she may just personally and discreetly send off thye dossier to avoid the fireworks that it will cause.

My gut feeling is that I should use the vous form, perhaps qualifying it meaning you the club officials, maybe "je vous demande (vous les responsables) .......... " etc.

Does anyone know of the correct way of doing this?

The problem is definitely not her, or indeed any of the members of the committee other than one particular individual who rules by force and intimidation.

[idun]

I would always vous an official letter.

[ericd]

Use "vous" all along this time but end your letter with a manual note such as " salutations amicales . Chancer." if it is addressed to her directly...but if it is likely that she copies that letter to members of the managing committee, just stay relatively formal with " veuillez croire, Madame la Presidente, en l'expression de mes sentiments les plus cordiaux".

[Gardengirl]

I would use the formal form throughout, and add a short separate note in the informal form, just mentioning that it's the club officials you are demanding to follow procedure, and that it's not her personally you're aiming it at.

[Chancer]

Thank you to you all, that is pretty much what I was considering, its good to know that I wont have to explain the vous as well, I create enough confusion already, in fact I often use it to my advantage in negotiations.