Carl, sorry, I posted new information on DVinfo over a week ago on this, I should have also posted here. The important part of an email from Tiffen Australia (on why mine is being delayed) was this information:
"the designers have up-spec'd the payload capacity of the arm to 24lb (11kg) to give the Zephyr a wider payload range and, just as importantly, to increase the camera payload when the new Tango is operated with the Zephyr. You probably know that Tango currently only operates with Zephyr. The second upgrade was based on a decision to design a vest specifically for the Zephyr rather than simply adapt an existing vest."
Also Robin are you referring to the price for the Tango or the Zephyr, surely the Tango won't cost that much? Personally I'm still scratching my head on how many times I'd need to use it anyway, so
I wouldn't be paying a lot for it myself.