I started with a 6.1 107l (me 82kg) and I'll switch to 5.9 92l after 6 months riding.
I would recommend a smaller board. 100 or max 110l are enough!
I perfer shorter boards  cause pumping is easier with shorter boards.

That's interesting.  How much SUP experience do you have? Did you learn on flat or choppy water, and how long did it take to consistently ride on the foil? I read that body weight + 30 litre is about right for a beginner with good board skills which would be 120 to 125 litre for me.