I used dollops of concrete under each leg - once I had got the alignment spot on. Dug a hole in the grass, filled it with concrete, placed a bit of plastic sheet over it, then, one at a time, I lowered each leg onto the concrete to make a little dimple. Then next leg, checking level etc very carefully. Worked a treat. Of course you never alter the tripod settings after this.
Put the concrete below the level of where the mower could hit it.
