Have you ever seen an aircraft TAKE OFF without flapping its wings?

The use of bird-flight (whether in ground-effect or free flight) is not a completely accurate comparison to a manned vehicle operating in ground-effect. A bird actually FEELS the air moving around and past it, and is capable of making fine adjustments and changes in its wing shape to counter forces. Morphing wingshape in a man-made craft is not currently within mans ability (apart from subtle changes through the use of flaps and stabilizers...AND...oh,yeah - Richard Drydens patented 'Transition Rig') >

http://www.transitionrig.com/

The lateral forces you mention are most certainly one of the largest problems to be overcome by the sailing aerofoil concept. "Never" is a long time. Sometimes what seems to be an unbreakable rule can be 'bent' to advantage.

Regarding ground-effect flight and sailing vessels, have a look at the accomplishments achieved by the Zero-G in 2001 >

http://www.spirityachts.com/sy-projects-Z.htm

Foxx