First up is a display where they fly three stacks of six kites each. Two of the stacks consist of North Shore Radicals, and the kites in the third stack look like Tramontana 2001s to me (please correct me if I'm wrong!).
And here's a display involving three stacks of seven Flexifoils each.
I must say, this second video does inspire us to try our hands at flying a pair routine with Flexifoil stacks. Start with stacking just two rather than seven? Less chance of a row with our bank manager as well ... Or maybe, given that we've not flown these Flexis before, we should just try them out first (can you launch them on your own?), and take things from there ... To be continued, possibly!