You've pretty much nailed the bonnet mounting method above, Nick.
The, ahem, comprehensive build manual disappeared during the Ribble ownership of the project (not sure if you kept up with the politics of the whole thing...), but it isn't exactly rocket science and you can pretty much make it up as you go along. There's always help to be had here too if you just ask - there's no such thing as a stupid question, especially when building a Sammio.
At risk of getting a load of oo-er, Missus responses, here's some pictures of my hoop -
I fibreglassed mine in to make it stronger and it's still fine after four years on the road.