Rewards: 56 Gold, R$56,000
Location: MASTER
Unlocks from: 28 Trophies in Open Sky Challenge
Maximum Required PR: 61.6
Maximum Required PR: 61.6
There are 45 events - 42 Trophy + 3 TT - with each car having a specific 2-event Showcase + TT. Only the Stingray can be upgraded enough to open the last cup races
On its own the Viper GTS can only reach 73%(!) - for 75% completion you need one of the others as well. Both the Shelby and the Corvette can reach 75% solo with PR53.1, but until we get the Corvette this is far as we can get***:
Gold progress rewards are:
25% - 7GC
50% - 11GC [PR <50.8]
75% - 15GC [PR ~53.1]
100% - 23GC
***unless you are a hacker 
