Would be the keel, you're thinking of?  Yeah, if you can, use regular wood, and seal it.  If all you have is the MDF, then seal it also, with a good acrylic, or epoxy. 

  I will vote # 1, because he has spirit, and is adventurous! 

  And I am sure he has a life vest. 

  Now just think, if you had all the money you have spent on this boat, you could take your Girlfriend, to a nice little Pub, and have a steak and kidney pie, and a pint each, while enjoying a nice quiet conversation, unless there is a soccer game on the telly. 

  Or you could buy more beer, and cook her parents the rest of the fox.  
  
     But I do believe it will float.  ........ for awhile at least. 

  Seal it well, sailor, seal it well!  And beware of the Great Whites that frequent the channel!
                                                                               Wayne