Gestalt, how much experience do you have?
Your avatar says you got a 1000 cm2 Levitaz foil, but not how much experience you got, and how fast/slow you can ride now?
As Dave says, so many other parameters can be more important than surface area, regarding lift and drag.
Also, it is not proportional, as there is always a "fixed" amount of surface from the part of the mast under water, and the fuselage, and the stab.
Besides, lift (partly lowend) is squared with speed of course, eventhough almost proportional with area for a give wing profile and outline.
Meaning, the smaller the wing, the less "advantage" in speed, unless you downsize the other drag parts (which one could with the stab at least)
IMO it might be nice for you to know these numbers, but it is really really difficult, and can only be done for specific wings and foils and riders.
Also, low end is just as much a matter of kitesize - as you can hang under a really big kite going superslow, even on a small fast racewing - if you want.
Peter