I don't know how to determine what you can safely pull but I can give you two points to consider.

1. Too much weight on the tongue will cause your front end to be light, therefore your front brakes will lock up and skid.

2. Too little weight on the tongue (i.e. to much weight behind the trailer axle) will cause the trailer to wag like a dogs tail.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.