Greg and all,
Fred in Alaska has pointed out an error in the axle layout I posted before - I had underestimated the width of the hub, so here is a corrected version:
You could still, just, get this layout to work, but you would need to increase the cutouts in the body that the end of the suspension arms would move into at full bump - it's shown with zero clearance, so it could do with being 1/2" deeper and 1/4" wider. The alternative is to get an axle with enough down start angle that it doesn't reach the body at full bump - but that's not easy.
Andrew