On Day-one Nambotin ended up 4th in E3, 30 seconds behind Samuli Aro who won the day. Not bad considering Nambotin gave up nearly 40 seconds to Aro when Nambotin fell in test 5.
IMHO, at least as far as the 515 thing goes, I doubt that Nambotin has the size to throw around a 515 to be competitve, especially in extreme tests. Its not that he couldn't win a test here and there, its that winning a WEC championship is all about consistancy.
Putting a 150 lb ex French motocross rider on a 515, just for the sake of having him on one, most likely won't put him on the podium. At least in the E3
class. Take a look at the above photos, Aro (#99) is on a two-stroke as well.
I would suspect that when an upcoming GP enduro's special tests look like they'll work well for Nambotin to be on a 515 that's when we'll see him on one.
Just my opionion.