I use a 6'6 Fish for really light wind (I am 72kg) !
(something like this
Goes so much earlier because it has a wider tail, and more straight edges near the tail
So you WILL gain a lot in low end.
But the price is, no doubt, that you have to move your rear foot VERY close to the tail (use a very wide stance in order to keep it gliding in ultra light wind if the wave dont carry you) if you want to ride waves and make a cutback with pressure and power !
Feels a bit awkward IMO, but is possible.
With your "regular" surfboard I am sure you will have a much more natural ride in the waves.
Just my view on things - you gain some and you lose some...
Kindly, Peter Frank