I just purchased an '04 XE 4x4 with towing package and automatic. Rated towing capacity is 5,000 lb. I am hoping to tow a 4,500 lb boat on an 800 lb trailer, and wondered if the Calmini add-a -leaf and HD torsion bars would be sufficient. It's a tandem axle trailer w/ brakes and a fairly light tongue weight (350 lbs). I appreciate any help.