Marek, I have a picture of a Morane-Saulnier pusher biplane floatplane which looks somewhat like a Farman. This one was entered for the April
1913 Monaco Concours International d'Hydroaeroplanes, with as pilot
Eugene Gilbert. Sure the machine differs at divers points from the machine of the Challenge, more than the undercarriage (floats) only. I have not looked up how the machine performed at the contest in Monaco, or turned up at all at the start
Cheers
Kees