I raced some more this evening/night 'to get my SR back up'. The races were great, the penalty system its usual self. I started at 71 SR, nothing but great races, ended at 46 SR 

 If you get bump drafted, it costs 10 SR again.
Any chance of SR gain is usually gone 10 seconds into the race. I'm starting in the back no quali, but never actually last. So 80% chance to get bumped from behind while avoiding the car in front. Thus the most to be gained from the rest of the race is -1 SR. One more time getting bumped, -11 SR for the race. Oh well, I'm at 35K DR, I wouldn't mind it to be reset. Start further back and lower incorrect penalties.
At the end, out accelerating a 787B by not shifting. All with that lovely engine sound.