I'm setup spring under the axle with a 3500# axle assembly. Axle width is 70" using a 6 on 5.5" bolt pattern. Springs are rated to 1750 each and I'm using a typical spring hanger kit. All from Rockwell American http://rockwellamerican.com/products. I'm running a 33" tall tire and the trailer is dead level with the hummer. Tongue height is around 19".