dwgriff1 wrote:The trailer weighs 580 pouns. I used a bathroom scale and the tongue weight was about 45 pounds.
OK. I'm assuming these numbers are for the empty trailer? And they were taken with the trailer at its normal ride angle (ie, not hitch down)?
That 8% (45/580) hitch weight puts the centre of gravity 6.5" (8% of 84") forward of the axle, if your hitch-to-axle length is 84". If you moved the axle 2" rearward, that 6.5" would now become 8.5", or 10% of the new 86" hitch-to-axle length. This would put your hitch weight up to 10% of the total or 60 pounds.
I'm not convinced a 8% hitch weight is a major problem - in Europe it would be considered more than satisfactory and many US recommendations are for 8-15%, so don't think 10% is some make-or-break figure.
If you are getting noticeable chatter, that sounds like a different issue and it might be good to recheck the tow line. It's a dumb question, but you're sure you haven't got a 1-7/8" ball and a 2" coupler, right?