With a couple of eye bolts,some cable,turnbuckle and a small piece of tubing,you can build a lightweight truss for the sides of the trailer,no welding.That will keep it from bending.
You really should move the wheels forward for that much weight.That will take alot of weight off of the hitch.
You want some weight on the hitch,or when you go over bumps it will want to raise the back wheel of the bike.1/3 forward sounds about right.You could try 50/50,might be a little twitchy.
If you have a straight axle on there,you could use u-bolts/j-bolt to move the axle anywhere along the side frame rails.
Last edited by Booger1; 05-16-11 at 11:44 AM.