I'd love to know. My E-cargo tandem with ten pounds of tools,
battery, MPie and 180lb rider easily totals 280 lbs ....
one rim got damaged by a pothole/sewer grate so I got a new rim
and new spokes from Gary (the old ones had done a winter)
the new rim went on very
nicely but I damaged it a few weeks later going onto a high sidewalk way to fast .
Took 90 minutes to get the back wheel off, true it with pliers and spoke wrench enough to ride home (whump,whump) and reinstall ...that's why I carry tools.
This time I've gone the other route and the MPII is at the local high end bikestore
getting a very strong rim installed with custom spokes . The way it was explained to me is that a really good wheel builder has to calculate the spokes to the wheel and
the chances of getting a rim to fit the spokes is very slim .... I'll keep you posted.
At present I have a new MPIII installed and the rig runs great .
Keeping the wheel from eggshape elliptical tendencies
due to the welding spot you speak of is a challange .
Trueing and tweaking by first loosening is working so far. To run as a two rider
tandem with a strong stoker I know that a stronger rim is needed.
Hope this is helpful ....steve