On the fifth lap you can manage around, but you'll lose +40 seconds at a minimum on race hards.
I found you can do 2 laps on softs, 2.5 on mediums, 4 on hards, 5 if you stretch but you lose +40 seconds
I lost the +40 seconds. It took a combination of 3 and 4 lap strategies and a whole lot of not taking full fuel load to get the lead back around an hour in. ymmv.
Edit: I'll add that I used a DS3 for this race and was harder on the tires then I would be using a DFGT an a proper endurance setup and strategy, it was a long day and I wanted to be aggressive.
Errr Double Edit: The GT-1 Turbo S2000 has to show up. Otherwise you'll be racing a RUF CTR which you will absolutely crush in that car. The S2000 is the one I had to beat, and he was gridded pretty high in the field.