So, given the time i spent making my wishbones, and the pickup ponts on my chassis not being ideal for the cortina uprights, I've been looking into doing my own.

been in contact last week with Rorty, and i've come about on a design with his help and advice.

Thing it, are SVA testers particularly keen on the DIY route? Is there any eveidence of their construction i need to gather when i do them?

No problem with sva if they look strong enough. They only do a visual inspection, not take them apart etc.

Funny I've been pondering about exactly the same thing - nice to know the SVA man is cool about it.
How did you modify the design? Most tarmac racers have the rose joint securing bolt that goes through the spherical joint vertical because the axial pull out loads of rose type joints is low and they can pop out under heavy braking. Rorty's design has the bolt horizontal which makes the upright very easy to build .
But tarmac racers have higher braking loads in the bottom upright ball joint from grasstrack racers which is what I think Rorty's design is for and I can't see a solution which is as elegant as the original but is suitable for tarmac.

I basically though of the same as the rose jointed one, with a suitably thick steel block welded top and bottom with a taper hole in it