With the Picatinny or newer Weaver one piece bases, you have quite a range in the possible location of the rings on base and scope. Assuming that your choice of spacing allows proper eye relief, is there any advantage to having the rings spaced farther apart, or closer together? Is there any rule of thumb about where on the scope tube the rings should be positioned for best support? Or should you just put 'em where you think they look best?