I'm currently 10 hours in this race and I'm using the Peugeot 908 Team Peugeot Total, by now I'm first with 5 laps over the Audi R8. Race started on wet, but in 6 laps it became dry and stayed dry until now. If you're going to choise this car, make sure to have a button to change headlights mode, because this car has very dark high headlights, while the normal headlights are more brighter and allow you to effectively see the road.
EDIT : I've just noticed that you have restarted the race with the Peugeot, good choice!
I'm doing a pit stop every 4 laps on racing soft (Out Lap - Fast Lap - Fast Lap - Pit lane at the end of the 4°), and I think this is the best strategy because it allows me to have a lap time pattern like that :
4:00 - 4:03 (Out lap -It depends on how much fuel you decide to put into the car, I usually refuel for only 32 liters every pit stop)
3:22 - 3:24
3:24 - 3:26
3:31 - 3:33 (Pit lane)
Plus this give me more stability and less stress over the race, and it's generally better than RM-RM or RM-RH in terms of times, because with a RM-RH setting I was doing 3:29 - 3:36 only for 4 laps, and Lap 5 I had to be extremely careful to not spin the car due to the worn out tires. So, the extra lap they give to you it's not worth the time you lose through the laps compared to RS-RS.