Sometimes it helps to see pictures. They have nice cross-section photos in Stringforum.net. I think the Head Rip Feel is more like the Isospeed Control, but I don't have photos of that.
Head Rip Control
Isospeed Control
The unique polyolefin ribbon is the orange part, which is on one side in the Head string and in a circle in the Isospeed string. In the Head string, you can see the ribbon makes the string irregularly shaped, which explains how the string generates more spin. The ribbon is wrapped around the core in a helical pattern, like a DNA strand. This is almost like a spaghetti string with an outer wrap!
I think it may also explain why the Head string doesn't have the tension loss problems associated with the Isospeed string. Let's assume that the polyolefin is the material that stretches and loses tension. Since it is helically wrapped in the Head string, stretching it would be like stretching a coiled phone cord as opposed to a straight cord. On the other hand, the stiffness properties of the Head string would be more like that of a traditional multifilament.