[alistairsam]

Thanks Larry.

Yep Sarge, it might move, but I thought having the concrete wide might help.
there's about 0.1 cubic metre of concrete.

I used a 5/8" threaded rod for the top plates and I levelled the jig at the base while laying the bolts so I didn't have to adjust the pier plates too much.

I'd also thought of placing a layer of stones before pouring the concrete, but then just went with it.
I might have an issue if I leave the counter weights on but remove the ota as that could tend to tilt the pier over time. but we'll see as its only 10kg.

Cheers