Well after reading the 90 or so post about materials including Gaastras I had a chnace to fly a GX2 16.5 the other day and it was sweet flying kite. Turns tightly and really smoothly for a big kite (don't really even need "for a big kite" qualifier on this one) .. not much change in power as it goes around the turn. Me and a friend had a takoon 17 and the 16.5 in the air at the same time and kept about the same upwind angles and same board speed.
The 16.5 has a smooth powerful feeling..maybe a bit more on the smooth & steady flying side of the spectrum than the takoon in my opinion, but it is not a slow flying kite.
In jumps it suprised me a bit becuase it did not yank me off the water hard so I expected smallish jumps but then it would keep liftng up and up for good high jumps in the 14-16ish or so knots I was using it in. All in all it was a pretty pleasant experience being powered by that kite.
The materials looked fine to me! but I think there have been enough posts on that