Hi Im John Ohlsens son Paul, good to find this thread, I can shed some light on a few things, and I will scan some photos at some stage too.
As to this post, Katipo was the name of the cars that Mark and Dad were building, the F5000 was a Katipo F5000. They also planned to build a bunch of Formula Fords, which were also Katipos, there was only one built and it was owned and driven by Mike Hole, it was christened the "Holesen". I have a stack of photos of this I will dig up and scan if anyone is interested?