I don't drive Race07 since AC ... but I still remember something:
- rain has never been so heavy in Race 07 as when adapting the GTR2 Autosim Weather Generator for Race07. ... We had a championship at the time in our league and it worked perfectly well .... as you may decide of your own rain proportion.
- I still have a mod for better Road Effects but don't remember if it might give the results you'd wish.
So try to find it under this name: Real Road Effects v1_40 by Denis Vorobjov
If you don't find it, make a sign by PM. ( I still have it but already noticed there still was a download link on the web.