If this can be of any help,
Here is my personal translation of the j.valles
“ Allo, I just met the owner of the Saphir (No 14) in Toulouse and which, like mine, in under construction (No 86) we got a long discussion about the aircraft. About the flight behavior he told me that the Saphir has a natural C.G. a little too far back and that he has added some 15 kg (33 lbs) of lead for a better C.G. According to him, the firewall should be moved forward some 5 cm (or increase the length of the engine mount) specially if (like I think I have read about that in a previous message) you plan to add the third seat. He also told me that the fin has got a few additional square cm of surface. About the former No 14, I built it as per plan. The upper part (I think) is to be built when the fin is mated to the fuselage. I will certainly be at it this fall, I will be able to give you more details then, if you wish.”
Yours truly, good luck
P.S. A personal note: I haven’t studied the Saphir plans, but at first sight, I would opt for a longer engine mount if you do not really need more leg room in the fuselage.