Funny he didn't mark it on the plan; he probably stated it in the text. I know he needed a lot of weight up front; there is practically no nose at all.
I think a lot of Deperdussin aircraft had constant chord wings, but this one didn't; the leading edge is straight but the trailing edge is not.
The usual rules of thumb don't always apply to early aircraft because many of them had large tail volumes, so a suitable CG could often be further back than you would expect. It's important to know because the plane is so hard to balance anyway, you don't want to use even more weight than necessary.
Maybe someone with the original article will show up with the answer. If not, I would use a calculator... Aircraft Center of Gravity Calculator
You need the kind that takes into account the wing area, the mean aerodynamic chord (MAC), the stab area and the tail arm. Just finding the MAC and using a rule of thumb might not do the job in this case.