With the same set up as Kevin I have stronger Kings and normal struts, ie not SLS, on the rear.
I have had some slight cracking along the left rear wheel inner arch which I have repaired and modified the rear RH well arch so as to prevent cracking in this area. This can be, and probably is, caused by the gross overloading required for such expeditions as the Simpson crossing and Cape York, such as extra fuel, water, fridge, second tyre and rim and second battery along with usually one passenger and necessary food, clothing and spare parts and tools. I have also installed a rear wheel strut tower brace to keep the rear struts in as near to vertical position as is possible.
The whole lot works well.