It sounds like I now have the second largest set of tires on this board. That's ok. Everbody I ride with runs 42's and 44's, then here I come with my baby 39.5's.
Anyway back to the topic at hand. I think that will be up to you. They act differently on various trucks. Mine try to wander if you put more than 15 pounds in them (with full hydro steering). That would be far worse with a factory power steering setup. Mine handles great at 7-10psi.
I don't recommend that you run those low pressures, just saying you need to play with it. Despite what some people may think, tires are part of the suspension. Now that you are riding on four big balloons you will discover that. Try it at 20 psi then change it up and see how you like it.
Also, go ahead and get one of those $12 digital air gauges from Autozone. They read 0-100psi in half pound increments. They are a lot better than the classic stick style gauges.