So I have been kiting for a few years, but mostly in cold water with little wind so still consider myself a beginner, but I am happy in choppy conditions or in the swell, but not so happy in waves - just want to get through them.
I learnt with a seat harness but see very few people using them. So I went and bought myself a waist harness and have been trying to get used to it, but I am struggling. 
How do you stop it riding up? If I wipe out in the waves or trying something new, the harness ends up too high. I have tried to pull it down, but can't seem to manage it with the kite still flying and don't want to have to land the kite just to adjust the harness.
Also, it seems that my body position has changed - I struggle to stay upwind in marginal conditions where I would be able to on the seat harness. I also seem to kick up more spray using the waist harness.
So my question is, is it worth persevering with the waist harness? There must be a reason why some many people seem to use them.
Regards,
Calvin & Hobbes
my suggestion would be, go back to the seat, when you start doing freestyle moves and riding waves, then use a waist, the waist harness will just give you more freedom. You should be able to hold more power from a seat, or just stay out for a longer sesh.
For most practical purposes there's little difference between a waist and a seat - assuming the waist fits, actually starts around your waist, and your stance is good. It certainly shouldn't change your stance. Waist's are however less forgiving of bad stance.
It will occasionally ride up in a big stack, if that happens, I can pull mine down lying on my back in the water with the kite at the zenith.
I started out on a seat harness and went to waist after about 7 months. I hated the seat harness, it is so much easier to get the board on your feet after a stack when you don't have those leg loops constricting you. I couldn't believe I hadn't done it sooner to be honest.
But each to their own I guess.
I think an important factor particularly with waist harnesses is that they really have to be a snug fit. Better a touch to small than atouch too big. That could be the issue. also I find I have much less harness movement when I am wearing my wet suit. The material holds better I think.
In summer My harness rides up more when I wear a rashie than when I wear a t-shirt. But In a big wipeout it always comes up a liitle.
My waist harness rides up in stacks and some jumps, but does so less if I wear more layers underneath (radiator + rashie).
If my waist harness rides up, I can get it back down with the power of the kite whilst riding. Just put the kite as low and powered as possible and lean back hard. Arch your back and you can sort of wiggle it down to the small of your back again.
I also found pulling a bit more depower on helped when trying to go upwind on the waist harness. I was riding too powered at times and my arms were stretching out too far. This was messing up my posture and not allowing me to twist and face upwind enough. Depowering a bit pulled my arms closer to my body for a better stance.
Forget the crowd, my Dakine Fusion seat harness is soooo comfortable. No chance of a wedgie unless you don't wear rubber underneath. Save your back.
Sitting in the water wriggling your harness down sounds like sharkbait to me.
Oh, and I have one for sale in size L (waist size 36-40) for $40. I've lost abit of weight and have stepped down to a medium.
I started with a Dakine Fusion seat and thought it was ok, but wanted a bit more freedom for toeside etc, so I bought a Flying Objects Flight Control waist harness last season.
I tried it a couple of times but didn't really like it, it kept riding up and just didn't feel right, the hook sits up higher which made it harder to reach the depower and I just didn't seem to be as balanced for jumping etc, especially when overpowered.
Over the next couple of months I mainly used my Fusion seat but kept persisting with trying the waist aswell, mainly when I knew I was having a short session as I seemed to get tired quicker and could feel it in my lower back.
Well by the start of this season I was only using my waist harness, I went on a kiting holiday in October and had about 4+ hours on the water every day for a week in 20 - 30knots with absolutely no back pain and no harness rash whatsoever.
I have not used my seat harness since and am not likely to ever use it again, the waisty is just much more comfortable and gives you so much more freedom.
I find that it hardly ever rides up even though I wear it looser now than when I started wearing it (so it will slide around when I ride toeside) and if it does ride up I just fly the kite real low, lean back and just wriggle a bit and it actually comes down or sometimes I just hook my thumb in the handle at the back and give it a little pull down.
I think what helped was that as your kite skills improve you can get away with a much smaller kite and you tend to ride with it a lot lower.
So my advice would be to persevere with the waist, you will eventually love it and if you don't I'm guessing you don't have a Flying Objects. 
Thanks for all the advice. I have a Cabrinha waist harness and had tried to slide it down when lying in the water, but not with the kite flying low - I will give that a try.
Also good idea to wet it first - I will also give that a try. I have been struggling to go toe-side so maybe the waist harness (when i get used to it) will help.
Can anyone tell me what the elasticated pieces on the harness are for? You have the velco that goes around your waist, but then on both sides there is a wide piece of elastic with velcro at the ends - I am not sure what you are supposed to do with these.
Thanks again for the help.
Regards,
Calvin & Hobbes
Not really familiar with those harnesses but it sounds like a similar setup to the dakine fusion whereby you do up the first overlapping velcro strap, then you pull the wide elastic straps with velcro on the end that are on either side into the centre and attach by velcro to the first strap just to give it more support and then you buckle up the spreader bar.
If that makes sense.
