You could do that, but not everybody manages money the same way. Is the goal purely to see who can pick more 50-50s, or to see who can cap AND manage money so as to amass the most in a set time. Cuz if it's the latter, then I think you have to risk the type of fluke or luck you describe. Not everybody thinks in terms of units, so you are cutting into their strategy some if you don't allow them to bet huge where they think they have an advantage, or to chase when trying to catch up.
I guess you could lose by a fluke, but I suspect that even within two weeks, if you truly are superior, it will show.
I guess it depends on what you and Harvey want to agree on.