There is no definitive Realfeel value for each mod out there, as we do not all have the same wheel; same controller.ini; same wheel setup in our Windows Control Panel etc. etc. It really is worth you spending an hour or two finding out the right Realfeel value for your computer setup and all your favourite mods.
When I want to find a good Realfeel for a new mod, I edit the "realfeel.ini" so that the console is enabled, as well as run Rfactor in windowed mode.
I then start up a test session at the full course
version of Oulton Park 2005. I put the console window to the side of the Rfactor window, making it as tall as possible. I then drive the track, keeping an eye on the "%" value in the console. From memory, I think that the biggest bump on the track is around the area of that first chicane. I then adjust the Realfeel value so that the "%" value never goes above 100%, using the Ctrl keys (left for 1000 jumps, right for 100 jumps) and the Numpad 7/9 keys.
If the steering feels really odd when trying to weave just off going straight, you need to hit Right Ctrl + Numpad 8 once to reverse the polarity of the Realfeel value.
Good luck, happy tweaking!