Hi,
I have a 68L twinfin (from 2009) for heavy wind days and I'm 72kg. The board functions fine in good conditions. However, if the wind drops in the swell (typically if the wind is side-on shore) and especially when there are large waves, I tend to take my 84L board. The extra volume makes it a lot easier getting out.

If I would buy a new modern board, I would take a 78L multifin, rather than a 68L