I tried to landboard the other day and I have to say its quite difficult.

How do prevent your board from going to far upwind? If you lean against the kite, the board goes upwind and just stops. If I try to ride with my feet flat then you cant lean against the kite and have no power. Pretty frustrating especially compared to water.

My experience with Land boarding is you gotta know your kite really well you need to know what you can and cannot get away with.

Landboarding is really really low resistance kiting. less then water, less then snow and problably closer to ice skating.

I always tell people the secret is your sides. you need to learn to dance the kite on the side of the window really well to generate a controlled power for landboarding.

I've noticed in landboarding there is 3 sides to the side pocket of the window. power, upwind, stall power is at 11or 10, upwind at 10 or close to 9 and stall at 9 and 8. newer kites are starting to fly deeper and deeper in the side pocket so its getting easier and harder at the same time.

What it sounds like in your case is your treating it too much like water or snow. you're putting to much resistance in the harness and edging too hard with the board. Its gonna be a combination of feeling less resistance in the harness and more flying the kite let out on the bar give with the harness, speed up. More resistance in the harness pull a bit more on the bar slow down and rail up wind. much much more subtle then water or snow you need to retrain your brain for these different power requirements.

Also dunno the board you're on but if its a really loose or even springs on the trucks that is not what you want. The board at speed wobbles way too much and just moving is difficult as the board always goes too far up wind when you don't want it too.

Spring trucks are garbage IMO, Skate trucks are better get different bushings and my favorite are the torsion cubes from ground ind.

In the begining wear lots of pads as you are going to make mistakes and hit the ground hard. when in doubt jump out and static fly.

Terrain can make a difference too. I learned on a alfalfa field prefer parks with low cut grass and beach boarding is a dream just stay on the the brown wet sand dry sand is trouble you'll face plant instantly.

I really like land boarding in the off season and if you become profiecnet you'll notice you can thread your kite through a key hole in other discplines.

Landboarding is really a game of finese you'll learn to calm down and not throw the kite around and be aggresive as with the other aspects of kiting. You may want to put some time in static flying walk with your kite know the wind and where you feel resistance bring it over head high and go the other way. and if you go down wind get the board turned quickly or hop skidding sideways on the tires defies physics and ends up in a face plant. take it slow you'll get it.

lanbro
You have to relax on the board and fly the kite in a more neutral manner and balance the heel to toe so you go in a straight line , slightly upwind ,slightly downwind when the wind cranks then you can lean on the kite. if the wind is light loop the kite straight downwind or on a broad reach to get used to steering the board where you want to go. Tighten your trucks a little and air your tires up to max and relax. CrazZ is right on with his advise

Thanks for the advice....I probably need a new land board as well. Any good boards for a 200 lb guy?

Craz Z already sumed the kite factor of your problem.
Regarding board:
You mustn't be centered to you board. Lean on your back foot and force the board forward (and keep it there), stretching your front leg.
Press down with the thoes of your front foot and the board will turn downwind. Also use the knee movement to help you press it (very similar to snowboarding if you ask me).

A very good method to getting used to a mountainboard is to go slightli downwind or at least sidewind and just trie to carv behind the kite and you'll get the fealing how to control the board.

But the most important is how hard are your trucks tightened.
I set it up on a small ramp, where the board is picking up speed constantly (on a flat surface). If it starts to wobble at some speed, I tighten the trucks a bit and trie it again. But you don't want to tighten it to much, just as much to minimise the wobble, there's the magic limit, because if you go tighter, the board will stop turning.

alot of good explanations above but the simpliest bit of advice i can give you is change your stance. you want an even stance between front and back foot not back foot heavy like on the water.

yeah the bullet is correct. weighting more 50/50. also steering the board is opposite stare with you back foot on a longboard. so i guess your weighting to hard an the back foot and driving hard up wind.
lastly controlling a landboard is all about sliding and drifting. if you can control the drift you have unlocked the secret...drifting and 30+mph is an intense and special thing.