RE: Carve 145 Fin Size
I cannot comment directly on the C145, but I do have a similarly sized Tiga Flash 74 and I weight about 100 kg. I have actually slowly crept down in fin size, and now find that a 46 cm Curtis SR-6b is quite close to the optimum when comfortably powered on a 9m sail.
I do also have a quite powerful 52 cm racefin from Fin's and it is really only comfortable in very marginal conditions.
The answer may be related to sailing style, stance, etc. Hard to say, except to say what works for me.