Hi Adran.... (small dig at spelling!!!! - but used to spelling mistakes on these forums)Yeah, a bit like figure 5, but with only two rings instead of four. This will be reasonably small, so a bit of precision and patience will be required. Once I get a design I am happy with, I will investigate getting them moulded in fibreglass.
BTW recognised the scan - I have that article.
Cheers
Graeme