we just got ours 32 cliff hanger rims and Sapim extra strong spokes on dt Swiss hubs about 400 pounds bike and us. we do light mountain biking. the wider rim caused our tires to hit the fender though.
I don't like 32 spokes for heavy touring or Tandem use. The longevity of 32 spokes is dubious with the weight you suggest especially on a tandem. I only agree with 36 spokes on the front of a Tandem with the larger diameter alternator hub and the strongest rims. The stress on the rear wheel of a Tandem is even greater than the front. 32 spokes on the rear of a Tandem sounds like taco time to me. On my Tandem I built two sets of wheels with Phil Wood hubs. I didn't own a car and needed the bicycle to always be ready. With 40/48 spokes and dishless rear wheels the occasional cracked rim was the only problem.