The best score I have manged to get so far is 5,907 and the gold medal (7,500) just seem unachievable without cheesing it by moving back and forth to get the additonal points. Not a huge issue and I'm sure it will not be too high in the fix list for this route, but worth mentioning nonetheless
I just searched the forums to see if anyone else was having the same problem with this mission. I've played it three different times now and I can't get anywhere near the target score of 7500.
I have the same problem too. It's not a big deal but for a person like me that gets PTSD if I don't get gold in every scenario it's frustrating.