I figured out a way we can enforce tires but it requires everyone signing up to RSR Live Timing and you'd have to delete any faster laps you might have on a leaderboard in order to show your slower lap on the stock tires. At RSR you can hit an icon on the right side of the list and see all the settings someone used, so I can even enforce the session settings as well, but it would require a lot of checking on my part.
2 problems though. I didn't make joining RSR a requirement before launching the contest so it wouldn't be fair to ask everyone to join now IMO. Next time around though it's a definite possibility. Second, RSR seems to be somewhat borked at the moment. None of the DP2 cars seem to show up on hot laps, or at least the ones I've checked. The
Vallelunga/Countach board for example, is blank. I shaved about a second off my M3 time at Vallelunga for the Pro Ranking a few days ago and it didn't save it either which would be highly disappointing after putting in a long or even a short session and making some improvement to your time. It was also displaying in game, lap times for that combo that didn't appear on the leaderboard when I checked through their website. Even running the Lambo for example, shows me in game that someone ran a lap of 53 seconds or something ridiculous, even though the leaderboard is blank online.
Hopefully they get the issues sorted out or maybe we can find an alternative. I think it would be a lot more fun in this car and others, with some harder tires.