Hi David, Glad to see you on the forum. A CBR 500 is plenty big enough for what you are doing. Some of the biggest riders don't take big rides, they take a small series of steps, typically fuel stop to fuel stop, or town to town, or some other metric that works for them and accomplish the ride that way. Hydration is important, you dehydrate even on cold days at 100 kmh..
Your BB2500km 36hr ride is a comfortable entry effort, just document the SS1600km as you go.