That's fairly close to the pressures on my wife's bike with 26" 42mm Schwalbe Marathon Supremes. 28 psi front and 35 psi rear.
Her bike weighs less than my Raven Tour (maybe 2 or 3 kg less), and she is small and light at about 44 kg, she usually has about 5 kgs of luggage.
I didn't drop the front tyre pressure quite so low as you because of the (perceived or imagined) risk of pinch punctures with the very flexible Supreme tyres.
My own take on tyre pressures is to start near the recommended maximum pressure marked on the tyre (generally too high for me, even with a full load) and drop gradually till I notice increased rolling resistance, then increase pressure a bit.
Exception for fat tyres - I start at Thorn's maximum recommended pressure for the size of tyre concerned rather than that of the tyre manufacturer, the latter is often high enough to damage rims with a high volume tyre.
I run my old utility bike with 30 front and 35 rear. This weighs about the same as my Raven Tour, and has 650B size 50mm Schwalbe Marathon Supremes. I weigh about 85 Kg and generally carry 8 to 15 kg of luggage on that bike.
