This is one of those jobs that if you don’t start you will never start. If I sat down and tried to do the math first I never would have gotten around to doing the actual work, so I didn’t the work and I’ll check the math later. After I get my bike running for the summer.
The modifications consist of moving the bikes back over the axle to take some of their weight off the trailer tongue. I used the center stand as a reference point to determine a practical center of gravity location for the bikes and the wheel’s axle for the CG of the trailer. I moved the spare parts to the area in front of the bikes knowingly negating some of the benefit achieved by moving the bikes but that spare engine isn’t going to be around forever — just until I strip out the parts we want to keep.
So far the trailer’s back hasn’t broken and nothing has fallen off. Success!