I have been having a little look on other forums and found some charts for it.
Not sure if this is correct but maybe someone can confirm.
I'm assuming XL on the tyre sidewall means extra load / reinforced since that's how i'm working it out.
Old tyres are load index 81XL
35 PSI on front which holds 876 Lbs
31 PSI on rear which holds 797 Lbs
So the new tyres which are load index 82
30 PSI on front which holds 901 Lbs
26 PSI on rear which holds 801 Lbs
The new tyres can hold more but don't want to lower 1 psi on front and rear as they will be 5 Lbs short on front and 6 Lbs short on back.
Seems like the new pressures are low but I guess I will try it and see how it goes.