This heim joint is a bad idea, as it has been used. No real race car designer/suspension engineer, will put a ball join in shear loads. The gems link above is the correct way to do it...
There are other ways to do it, just look at the whiteline ball joints for imprezas...
Fabricating a pair of wishbones isn't that hard...but it changes a lot the suspension geometry. It's not that through the top mount you can "reduce" camber. Scrub radious, roll center possition and camber gain characteristics are affected, a lot...