I have just purchased a bj60. It is my first 4wd and I want to put on bigger tires for a little more ground clearance. It has 31x10.5x15 on right now. What is the pros/cons to switching to 16in rims or should I stick with the 15s and what is the biggest tire you can run without doing any mods.? I often carry heavy loads through very poor "roads" in the jungles of borneo.