[ODE] How to keep capsule stand and how to make it hover over below objects at a certain height?

[michael kapelko]

To make capsule stand, I make its angle always of 90 degrees. But 
sometimes when some heavy box falls down onto it, it lays and when 
setting to 90 degrees, it becomes half inside the floor.
To make capsule hover at a certain height, I tried to add force along Y 
axis (this points up), but this makes the capsule constantly jumping. I 
tried to dBodySetPosition (body, pos[0], pos[1] + 5, pos[2]), but then I 
get the error: ODE INTERNAL ERROR 2: invalid operation for locked space 
in dGeomMoved(), I also tried to dGeomSetPosition, but this causes error 
either.
So now I wonder how to do it.
I there exist several articles which I read, including the 3 ones in ODE 
FAQ.
The only formulas I found to keep capsule stand are:
   AV = get angular velocity
   R  = get euler rotation
   R += T * AV
   apply torque( -R.x * C, -R.y * C, -R.z * C )

I didn't try it, main problem is hovering. And I found nothing concrete 
about hovering.
Can anyone help me?
Thanks.