I have been working on it's development. I have been using one, albeit a prototype, for foxing and stalking as part of the testing.
The Hunter Pro is far more stable than the z sling, particularly when crossing gates and leaning over fencing. There is more to it than the z sling so it takes a little more effort to get used to it, but once sorted its simple enough. It does not have the long tail on the stock, so it's less likely to get caught in quad sticks, when they are deployed or closed. It also will not get caught when cycling the rifle bolt. This feature for me was a big bonus as my z sling is often getting tangled particularly at night or when it's windy. It's a little more expensive than the z sling but it does include the swivels and as a bonus it's made in the UK.
Whilst I have had a small role helping on the design I have no financial interest in the product or indeed the company making them.