Trading on the under 4.5 goals

[Guest]

I have been pursuing the under 5.5 goals, and cashing out before there are five goals. I built up to a nice amount. However, the other day, I left the trade too long and there were five goals. I had staked half of my winnings.

When should I have traded out of this match? Should it have been after four goals? What is the best strategy when using the cashout on Betfair?