Our son, over six foot tall, sleeps happily on a diagonal, in the upper bed in our 600. Slightly shorter, I recently spent successive nights on the passenger seat, swivelled and fully reclined with my feet on the bench. We infilled the gap with luggage and cushions, and I slept well.
I've commented on the van before, and the only update at fifteen months of ownership, is that it remains well put together, an easier drive than our previous Euro 5 Ducato, love the fridge, the only issue being that a step is needed to access the rear bed which then blocks the bathroom door.
The convenience of any warranty and servicing being done by one company is a bonus - previously vehicle servicing and conversion issues were dealt with separately.