He must have meant in back of center. You want 60% of the weight in front of the axle.Why 6" past center for the axle? Not sure if you mean 6" forward of the center of the bed or aft of the bed center? Confused by the way you stated that. I have noted with interest there are many variations of axle placement on trailers. This includes both single and dual-axle models. Some have the axle placed far to the rear and others closer to bed center. I have not seen a good write-up on the pros and cons of various axle placement philosophies.