I guess you found out by now

It really depends on what you want to achieve. If you want to 'hedge' them then one metre spacings in a line is good. If you want a natural look over an area hold as many beans as trees and stand in the middle of that area and turn around throwing up beans with your eyes shut to get a natural look. Or if you think you can achieve a natural look without that then just avoid equal spacings and placing them in lines. Even two in the same hole will help to give a natural look.  If the plants are all the same size you can plant any amount in a given area and cover it that much quicker. Trunks don't take up much room.

However you can't change your mind over time because an established tree will shade out small ones planted within its range. A look, with eyes open,  at a natural forest is always a good idea.