How much is too much weight on rear of 130 tray

Hi,
I'm not sure how much the Dual Cab impinges on the space available where I put my spare tyre (mine is a D130 cab chassis) but I mounted mine under the tray, forward of the rear LH wheel, and there is more info here

https://www.aulro.com/afvb/images/im...013/11/882.jpg

cheers

Same as what Velt said. But if you add another axle????