Hypothetical scenario:
You can bet on a single dye roll (choosing a number between 1-6), but if you win you get paid x12 of your stake (instead of x6).
So the Expected Value is positive (see example below), but you'd still have 83% chance of losing.
1 - will you take that bet?
2 - if so, what % of your available funds would you put at stake (i.e. funds you're willing to gamble and afford to lose)?
Again, this is a single, non-repetitive bet.
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Simulation for BTC1 bet:
EV = (83% x -BTC1) + (17% x BTC11) = +BTC1.04
Edit: calculation corrected, credit to Saint-loup
I think by asking if somebody should take the bet in your hypothetical scenario, it misses the point of why we should take spots that are +EV. It wouldn't really matter if you're just allowed to be in a +EV spot just once then nothing. It's about the long run and taking on enough of these spots to make some profit.
But if you're just asking for the sake of asking..? Sure, why not, it's like a value bet for a mispriced underdog spot in sports betting.