This is an anecdote that I love to tell. Last month, I decided to bet against San Marino in their Euro Qualifying game (they were playing Northern Ireland). They had a 1.01 payout line. So I bought ten proline tickets in-store at $100 each at a Circle K. The next day, I claimed my winnings. I had to walk from store to store/gas station, claiming no more than two tickets at a time because each store only had so much money up front. Long story short, I bet $1000 to win $10. This must have caused OLG to prevent further hooligans from being able to make big bets on such steep payouts in-store.
Earlier this month, I tried with Women's Ice Hockey. Finland against France had a 1.01 payout line posted online for Finland moneyline. Nonetheless, that option wasn't available in-person. Finland vs Sweden had a 1.04 payout line posted online for Finland ml, which also wasn't allowed in store. Germany vs France however, had a 1.05 payout for Germany ml and was allowed, which I cashed in on. Therefore, I deduce that the cutoff for the steepest in-store proline bet is now 1.05.