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Kami said..Salut colas, please what C-drive fins size do you reckon to my 78kg and my homemade shortSUP as the last red one or my next minion type 7'27"90liters as shown here

I use the sizing chart:
www.cdrivefins.com/pages/Sizing-Guide.htmlIn your case this means M, like Reprobate said. I use XL. A 85kg friend is loving his M. I think you can undersize them a bit, but not oversize: I use L when I want a bit more looseness, they still have plenty of grip.
For the rear quads, QS or QM depending on the kind of "stiffness" you like under your rear foot. I use QS in small to medium waves, QM above.
The ultimate C-Drive quiver would be a thruster + quad set, and the twin+trailer set, for a "simmons-ish" ride with twins in the rear quad positions, great for wide tailed boards in non-hollow waves. And the small trailer is great for a 5-fins or 2 1/2 configurations.
At the least I recommend a thruster + quad set to try them out.
I have put the c-drive twins to replace the keel fins on my 6'10" Simmons SUP, and they provide as much grip, but noticeably better acceleration and "squirt". The keels were kind of holding back the board on fast waves.