Hey Dachopper,
Last season I raced, I used the 18m VMG2 as my big kite. I found it was perfect for me in anything from about 6 knots. Now, having said that, I was not looking to dominate light wind racing. In Perth, It's pretty rare that we get winds that hold in for long at below 10 knots. Especially in summer where it tends to just be ?n or off".
I would comfortably hold onto mt 18m in 15 knots and it still be very manageable and fast. If just free riding. then you can reach in as little as 5knots. Gybes and tacks need to be on point at this wind speed, but the kite will fly just fine in 5 knots.
The original VMG series was a lighter kite because it didnt carry the weight of the fibreglass rods. The VMG 21 would fly in as little as 3-4 knots, and I have ridden in 4-5 knots on it. It had a much narrower wind range that the VMG 2 and I would find 12knots about max and at 15 knots I was in uncontrollable lofting/paragliding mode.
I am selling my full quiver of VMG (21, 15, 13, 11, 9) all fly perfectly, and I may even be interested in selling my VMG2 (18, 13, 10). The wind ranges on the VMG2 are much wider than the VMG, as both quivers covered same wind range alneit with fewer kites in VMG2 due to wind range overlap.
Having said all that, light wind foiling depends a lot more on rider skill than kite choice. A fast efficient foil, with longer lines (ie 17-20m) and a rider with good experience, will get foiling easily on a 10m foil kite in under 10 knots. I've done it with my 10m Soul on a Core SLC freefoil. However, If you are racing or looking for ultimate speed downwind, that's where the big kites come into their own, you need to have canopy to edge against to generate speed and apparent wind angle.