Actually I think I could have made a serious error in my weight calculations with the bags of rubble. So I'm going to try it again tomorrow with a more appropriate substitute for Gareth
With a few mods to the kit I can now rig it up in a couple of minutes. It's much better than my aluminium slider tracking gauge, thats heading for eBay.
I can imagine the fun you had explaining it to the Chinese engineers. I bet they were taking notes while you explained.