I've tried 47 AI on the Nordschleife a few times, didn't go too bad, patience is golden! I always started at the back of the grid and there was a couple of traffic jams towards the start from someone loosing it, but if I don't try to win the race in the first couple of miles the traffic thins out and the racing if fine. Haven't tried a multi-lap race to see if there's a chance of catching the leaders. Performance isn't bad either, with 15 AI and starting from the back, I was getting about 68 FPS then 90-120 for the rest of the way. With 47 AI, again starting from the back, I was getting 55 FPS at the start then 70-110 once things spread out (UltraWide 3440x1440, everything on max). The load times for me aren't any different with 15 or 47 AI, timed at 50 - 55 seconds every time tonight.
Not directly related to gameplay but something that big grids could really benefit from : better replays to catch the big scenery wider. The Raceroom camera is usually too close to your car. What I find great in Assetto Corsa is that you can chose replay from (superb) fixed cameras only. Raceroom has those cameras but their use frequency is too low in my opinion. Raceroom has really the potential to deliver epic replays.
before the patch everything was fine with like 26 cars, when I go with more than 19 cars now, there is a huge game freeze every X laps.
Everybody, do not forget that meanwhile it was to be read that huge AI fields come at the cost of reduced AI competence, the criterion for the first such degradation is I think 30 cars, a second one akes place at - I am not certain - 50 or 60 cars. Thats what I was told some time ago. Its not a dramatic letdown, but a noticable one , and I could imagine that it could mess with the statistics calculations of adaptive AI as well, maybe? I always cap my car fields at 28. With me, that is 29 cars then. Just to be safe. With adaptive AI, I also always flow in the middle of the pack, so have always cars before and behind me, so whether out of sight there are another 30 cars is of no visible difference to me. It does not matter. The replays also work erratic only for me, last time I tried, with too many cars: there always were the occasional invisible cars that the camera fixated on. Broke the immersion. Technically, I could run car fields of up to 50-60 cars on my rig. But for the above mentioned reasons I would recommend to have a maximum of 29 cars, player included.
Be aware that I haven't updated this for a long time so probably isn't completely accurate. Some circuits have been updated since.
To be always up to date: When you are on your dedi config webpage, press F12. Look for the network request "all" and browse the Tracks path in the response. (I used chrome for the screenshot)
Here's a crazy, half-baked idea..... Don't allow hosting access to the big grid MP to the average Joe. Keep it as a Sector3 thing, that way the people who are looking for some massively multicar online action will have a single place to meet. Sector 3 could rotate the cars and tracks etc, hopefully with a schedule at least a week in advance. Otherwise, as noted, we might end up with 50+ grid slots and still only a handful of cars. It could also be policed. (Maybe by selected volunteers from the forum.....) As I say, half-baked.