The very essence of gambling in the first place is to win and maximize profits from your wins, so every opportunity the game avails it's mostly expected yo use it judiciously as it doesn't come often because the casino will not pardon you either if you loose on any bet they don't make refunds rather they take it's as their own profit made from your bet which you placed.

In essence I'm saying if I am faced with such opportunity my straight answer is a big yes I will make good use of the opportunity and stake as much as I can afford to lose just if it later turns against me, because there are occasions the casino has taken from me not minding how I will feel so if I see such opportunity to stake on a fixed game I will stake an win

In other sense I don't see you staking on a fixed game tip you received early before the game commenced as been bad, rather I see it as an opportunity because the intention of the people who gave you the tip is for you to win so why should you denied yourself of the opportunity to win because you feel it's not right. To add, I don't think it's not right because that can't be seen as cheating or stealing.