Blue flags( a.k.a. the "courtesy" flag)) are not mandatory in sportscar/endurance racing... guys honestly, understand this ! It is quite an important part of sportscar racing... no need to freak out over a blue flag and do stuff you wouldn't otherwise, you will not get a penalty !
Just keep your head on, and when it is safe, facilitate a pass if he is that much faster then you.
To break i little bit earlier but very carefully does not mean to freak out and Rfactor2 does not make a difference of the situation its not real live with marshalls which decide about the situation, it counts only the seconds after showing the blue flag first time and the time is very shot.If you wait only one second to long you have to pit for 10 seconds. In real life. you can see so many racing actions like this otherwise the drivers get a penalty for blocking. I wish you the same situation, a driver who is very slow in lapping you, i will see what you will make.