I used the trailer body from Keystone with the Lindberg frame and thought it did a good job of capturing the feel if not the exact details of the trailer. Still, it might be something to consider as a starting point.
Like you, I was afraid of the angle looking wrong or (worse still) keeping an axle off the ground, so I hinged the whole rear of the frame. It's completely hidden by the trailer body, but allowed for last-minute adjustments and has enough slack to make sure every axle is on the ground.