Definitely sounds like a bit of overfilling combined with nose down attitude meaning more petrol going up the breather tube plus a bit of heat expanding the air in the tank forcing the petrol further up the breather, and indeed out the other end of the vent hence the spillage. Open the tank up to let the pressure out and try again. Might take a couple of rounds of running it a bit rough then repeating the switch off and open the tank routine before it will run smoothly and any engine warning lights to go out.
What's the phrase?..ah yes, "they all do that sir"
Good luck with it.
