Yes, but who's to say Zagzoo isn't modifying it to an example of a Prototype? Or that maybe he just wants to run a 4 blade prop on his engine because he can?
I did a Google search for "XF6F-6 prototypes" and this was the second page displayed:
http://perso.wanadoo.fr/christophe.arribat/stoff6f.html
3/4 the way down is this picture and an explanation.
Richard you have a lot to offer this forum and are very helpful but might I politely suggest that, in this particular instance, the tone of your reply was slightly condescending even though this may not have been your intent. jomodguy was quite correct in his statement.
We all learn something new everyday, that is what makes this forum so good and why I come here.
Cheers
Da Orc