Hope this hasn't been posted before but I thought I'd alert you all to the fact that Gallica has started putting online the French army's Revue d'infanterie. As the tanks were subsumed into the infantry arm post-war there are a lot of articles about the French tanks in the war. Of course, it is all in French but some material is quite accessible even with limited language skills.
Do you know if it will include prototypes, or only production vehicles? I'd be interested to know more about chars FCM21 and D3. The info on them on the Chars Francais website is limited, and I believe the dimensions given for the FCM are ropey; Wikipedia actually has more believable dimensions, at least for length, but it is not much more than a footnote in the Char B1 article.
The answer is no, these articles cover the tanks used in the Great War and are more historical studies, although the Etude technique article above has a number of technical drawings in it.
I discuss the Société des Forges et Chantiers de la Méditerranée (FCM)tanks in my forthcoming book, that is the 1A, 1B and the 2C, as well as the Schneider CA3. However, these are mainly discussed in the context of their impact on light tank production and the politics of their construction.
The best secondary source on the heavy tanks is FJ Deygas, Les Chars dassaut: Leur passé, leur avenir (Paris: Charles-Lavauzelle, 1937). Alas, this is not available other than in print. The Imperial War Museum has a copy, available for anyone to consult.
If you are looking for technical specifications (other than general ones, weight, height etc) the only palace to go is SHD/Vincennes. Carton 16N2124 contains;
Etablissement du programme de chars lourds en 1919, spécification, plans et renseignements divers concernant le char 2 C, à propos de la cession des chars anglais, études relatives à des chars non adoptés, 1917-1919.
I've only taken a brief look at this carton (as it wasn't directly pertinent to my research) but I can confirm that it has a lot of material in it.