There are many things about sportsbook and casino that I do not think fair but at the same time they are business institute, they run by their terms. When big companies find a user is trying to take advantages from them, they starts limiting the users. For that reason it's impossible to continue such betting [taking advantage, group betting, arbitrage betting] with big sportsbook but with small sportsbook I think a professional gambler can take the opportunity easily.
No
The smaller sportsbooks limit winners much faster because they are generally risk-averse and a lower volume of bets makes it easier to spot long-term winners.