H&R for example has c4 specific adjustable bars. You can even use stock end links too. 1,2,3 done. No fuss.

 

Just looked at them. They are 24mm but the 3's are 27mm. The sways I have are already 24 but fixed. What to do....

 

The H&R c4 front is 25mm, rear is 24mm. But consider that this just the physical size and solid bar. The adjustable holes will allow you to effectively make them stiffer.
Bigger isn't better, tuned is better. There's a reason why the C2 model is slightly bigger at 26mm front. The AWD version doesn't need as big bars as the RWD.