mcbee, thank you for your help.
i am going to lay at over 2.5@2 ,not at 2.02, and waiting, if matched then lay at under 2.5 @1.99 at once. it will make some little profit. then do it again.
the over2.5 price could be between 1.5-2.5.
also, it will run before turn in play and stop before the match start.