... a quick market product research about PFD/buoyancy aids that are compatible with a seat or waist harness:
a) PFD with a high harness hook hole:
http://www.npsurf.com/products/prote...ion-vests.html
http://www.neilpryde.com/accessories/vests/vest.html
http://www.npxwetsuits.com/index.php...182&Itemid=111
http://www.prolimit.com/impact-float...tandard-waist/
http://www.prolimit.com/impact-float...t-short-waist/
b) PFD/buoyancy aids that are compatible with a waist harness:
O'Neill Superlite USCG wake/waterski vest (4 buckles, no front zipper, bottom buckle may be left unclosed to ease access to high harness hook)
http://www.oneill.com/#/men/europe/c...t/black_white/
http://www.prolimit.com/impact-float...m-half-padded/
Caution about so called "kite vest" or "impact vest for kitesurfing" : they have very low buoyancy/flotation capacity, much less than 50 N:
http://eu.dakine.com/p/windsurf/harnesses/surface-vest
http://stores.wetsuit.com/-strse-Acc...Categories.bok
http://www.ion-essentials.com/conten...eoprene/vests/
c) kayak-designed PFDs :
http://www.kokatat.com/products/pfd.html
These kinds of PFDs are fine with a low hook racing seat harness type. Problems I see is that they are too bulky to be worn over a waist harness and the presence of a front zipper might severely hinder/reduce the free access to the high harness hook when windsurfing.
Cheers !
JM