To add to what Scott M. said in
his review of the RF Solo, besides a great WW IK both the solo and tandem ARE indeed very good for flatwater paddling as they simply move through the water faster than an AIRE or other IKs. They paddle well into the wind for an IK, and are VERY responsive.
Not constructed of the same material as the AIRE IKs but the ZOIK is also LESS expensive and simply fun for river running. Your butt stays above the drained water line, unlike the same price ($1,000) SeaEagle WW tandem which has you "sitting" in several inches of water at its lowest drain point all of the time with the drain plugs open for WW. I certainly enjoy "getting wet" going through the rapids on a hot day but I don't want to sit in cold water an entire trip. The ZOIK RF has the arched floor which adequately drains away the water.
In my opinion the RF solo or tandem is a great combination Whitewater and Flatwater IK.
