Yes, for your very light wind conditions, a larger rig makes sense.
The GO 141 and a 8.5 m2 free race sail might get you planing in 10-12 knots (5-6 m/s).
You will be ready for the larger sail when you get to a skill level where you make nearly
all of your transitions (tacks and flare jibes).
With your 7.0 and some pumping you might get planing in as little as 6-7 m/s (12-14 knots
at 70 Kg.
Hope this helps,