Fixed fraction, always
Two percent of current bankroll per ticket, recomputed weekly. On a $5,000 bankroll that is $100 of risk per position — not $100 of contracts, $100 of distance-to-stop.
Recomputing weekly rather than per ticket avoids the trap of shrinking size mid-week after a loss and then over-sizing after a win.
Weekly loss cap
Six percent of bankroll in a week ends the week. Three full stops is a normal outcome in a variance-heavy sport, and the cap exists so a bad Sunday cannot become a bad month through chasing.
No exceptions for Monday night. The cap is checked before the ticket, not after.
Why quarter-Kelly
Full Kelly is optimal only if your probability estimate is exactly right. It never is. Quarter-Kelly gives up roughly a quarter of theoretical growth and cuts drawdown depth by more than half — which is the trade every part-time trader should take.
Practically, quarter-Kelly on an eight-cent edge lands close to the same two-percent risk the desk uses, which is why the two rules rarely conflict.
Fees are part of the edge
Exchange fees on prediction markets scale with contract price and typically cost one to two cents round-trip. An eight-cent edge is a six-cent edge after fees. Any threshold you set should be set post-fee, or you are trading a number that does not exist.