I use this one I found on youtube
Only change I made was to nudge top speed down to 18x mph
It is so stable! Even with DS4 you can easy get 1:46:xx laps. Only need to brake a bit at the 100m marker for the first corner, take it at 125mph. Turn 2 & 3 full speed.
I'm the same, about 45 mins on a weekday to get my mileage and mess about a bit using the DS4.
Friday and Sat I'm on it a couple of hours so they're my proper sessions using my wheel
I've got all the N class cars except the two unicorns. At the mo I'm having a good go with each in turn, it'll take me a while to get through them all though
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Good luck and happy driving!