Thanks for sharing the results.
I agree that you should go to a lighter
oil. Assuming your 20W50 is the same viscosity
oil as sold in the USA, that is still on the high side in my opinion. Using heavy
oil like that, I would be very careful letting the engine come up to temperature before reving it above 2500 rpm.
That is a very big engine to spin over 7000 rpm. Unless all out racing or money is no issue, I would keep it below 6500 rpm and try not to do more than 6000 rpm most of the time. 7000 + is a lot of momentum to break parts with, should something go wrong. The more time it spends up there, the more likely it is for something to go wrong. But maybe I'm too old and no fun.