Stan's running a der kaiser with a sl rim and im pretty sure his is seated properly.
It's not something silly like the bead is sitting on your rim tape in certain places on your rim is it? that's the only thing i can think of off hand :/
You would have to either buy a new freewheel and use the broken one for spares or source another broken freewheel and hope the parts you need out of it are in working order.
You can't buy the parts for the echo freewheels im afraid.
Use a light grind, try not to drag the brake too much or get any crap on the rim. Always seemed the best to get the best results for me with most pads.
Hope this helps