PBP is demanding for velomobiles because of the distance, and the sustained high speeds. That seems to expose some of the shortcomings in the steering mechanisms. The other main complaint is aerodynamic instability in crosswinds.
The first interview I did of a velomobile pilot was Hans Wessels, who did 65.27 hours in 2003. I got a couple of interviews this time, and we put two velomobile related interviews into the 2015 film. Just because the rider starts in a velomobile doesn't mean they'll finish in one.
The early PBPs put seals on the machines, as the event was as much a test of the machine as the rider. I'd love to see Hajo's GPS data. Is it on Strava?