You should look in src/tables.c at the energy table. Basically, speed above +30 is of very little value, except you might want +40 so if you get hit by brain smashing or inertia you are still +30 after the -10 penalty.
Thanks you for your comments and tips.
So basically your telling me that any speed above +30 is actually unnecessary?
If that's true i can switch Feanor to Thror or even Ringil to The Great Axe of Eonwe?