https://www.erard.com/en...
There is a picture with a diagram in the product images, the AF 9 55 inch is 8.6cm thick, and weighs a little more than 23kg, so according to the diagram you are already off the chart and therefore the StandiT 400 is not suitable, so have a look at the 600 dan (should there also be such a diagram for the 600 on the Erard site).