That looks a bit flimsy for a 400mm lens. A 5 leg section 1 series?
The weight rating matters little as I am sure it will support the heaviest Canon/Nikon lenses quite happily but it is going to be very wobbly with mid to long telephoto lenses.
When I first got a 400mm lens I had a Manfrotto 055 XB Pro and it was pretty hopeless. It could handle the weight easily but it simply could not cope with the focal length (vibration damping). The Feisol Tournament model that I suggested above is the absolute minimum that I would consider adequate and then only just - but it is a very nice little tripod.
A Gitzo G1329/1327 or (better still) a GT 3530LS would be my suggestions but the OP lives in the US so cheap used Gitzo tripods are not on the list
Just my thoughts.