And +3.5° of caster?
0 camber isn't helping, a little bit of negative camber will help keep the car heading straight. If you could get a -.5° camber that might help some. I'm a little surprised you could only get +3.5° caster with the QA1's, but you're not the only one that hasn't been able to get a ton of positive caster with them. 235's aren't overly wide, tracking issues usually become more apparent with wider front tires. But I like to run more caster than that. Granted, I have 275/35/18's on mine, but I run +6.5° of caster on my car. That keeps it nice and stable and straight ahead. I've run it with as little as +3.5° and as much as +8°, and with 275's and my ride height and suspension around +6.5° was the sweet spot between the car being nice and stable and it not adding a TON of steering effort. Past +6.5° makes it exponentially harder to steer. Less than +6° and it would start to track around a little more. But again, that's with 275's not 235's.
Before I bought anything I'd see if you can add a little negative camber without sacrificing a ton of caster. The caster is ultimately more important, but that zero camber thing might be hurting you more at the moment. Even -.25° would be better.
I run Bergman AutoCraft SPC UCA's on mine though. You definitely won't get to +6° with the non adjustable QA1's.
