The Tokico 6-pots which are mounted on many Suzukis and Kawasakis are not an upgrade. They need more maintenance, are more difficult to bleed, cost more but don't perform better than the Nissin 4-pots on your GSX-R. The stock Slingshot brakes are very good if maintained correctly.
Nissin 6-pots (Kwak ZX7RR for example) are better but more difficult to find. And also a straight fit.