oK we have all seen JB froth man reviewing wings. Typical of those with a vested interest they find these are the best things since sliced bread. Looks gay as feck to me.
Soooo, I got a 2 hours session on the 4m Duotone today. With a 6 10 Fanatic Air and Axis 920. I can sup foil, kite foil and used to windsurf.

Found it super easy to putt around in light wind, not foiling , just like a windsurfer in light wind and stay upwind. Could light wind gybe ok straight off. These are easy to use. Couple of tricks for new players - do not let the trailing edge dig in and do not lean back like a kite or windsurfer.
With a few gusts I got up like the vid below I took of Jas from WAsurf/westOz.
+
super easy to use, simple setup,
not as hard on the body as I thought it would be, enjoyable
-
downwind hard, needs more wind than expected, blocks your view like a windsurfer, flaps around heaps when on leash
!
Boom is the way to go I think, super controllable
Can see noobs liking it on a sup then progressing to foil.
Bottom line - Even though I thought I would hate it I have ordered one. Agree with Naish that a 4 is all you need and I am 105kg (disclaimer- as long as you have wind over 12 knots). When would I use it? Light to medium wind small swell. Straight after work when I cannot be bothered to set up the kite.