they are exactly the same principal as the knock on wire wheels that have been on road cars since before the war, they are just held on with a central spinner thats just tapped on with a leather headed mallet not even torqued up like the centre locks. The important part is that on the near side the nut is reverse threaded so that with forward motion the nut is actually trying to tighten itself on the move not come loose.

Done properly in the correct materials they will be fine, I agree with Tony though I have seen pics of some very weedy looking adapters normally on continental cars, the ones we are all using are made from aircraft spec H15 7075 alloy, the stuff landing gear is made from.

Ryans the test mule though on his current road trip to the ring and back hopefully he does not end up with three wheels on his wagon.