I got this drawing from a guy in England who seemed to be close to the source. He was using this design on a full bodied racer of some kind but he said it had a very similar suspension to a Seven and didn't see any reason it wouldn't work well on one. So a disclaimer is in order here as I have no experience with it yet myself.
I chose to build mine by welding it out of 1/8" thick flat stock but milling the parts from billet stock might prove to be a better way if you could afford the cost.
If you chose, as I did, to weld it up, the holes where it bolts to the chassis have to be sleeved to prevent crushing. This is not all that clear on my drawings. I made tha parts about an inch thick overall.
On the upper hole on the triangler piece, when I made mine, I moved the sleeve up a little and cut two pieces for the top. Instead of bending a piece over the sleeve I welded the two pieces into the tangent of the sleeve near the top.
I can't remember why I had to do that at this time. Maybe it ws just easier.
I was told by my source that the 1/2" offset here is important but he didn't alaborate on why. I'm just passing it along.