Hello Scary Des,
You will know more than most if you test these devices professionally.
We had a problem with thieves using oxyacetylene (porta pack units) to cut off wheel clamps, hitch locks, security posts, chains, even steel gates and fences.
Even secure storage sites are being targetted by professional thieves and there is very little to resist oxyacetylene cutting gear, with caravans, industrial plant and trailers being stolen 6 or eight at a time. This is big business.
We believe it is impossible to stop thieves with wheel clamps and hitch locks, even though they are recomended by insurance, police, and the industry in general.
Look at the hublock which bolts directly to the wheel hub; our tests have proved it to be secure against oxyacetylene, "Stihl" saws, angle grinders, welding, drilling and professional removal tools.
I came across your posting through a Google search (old posting) but thought I should make you aware of a newer and effective security device.
Please call me personally if you would like further information.