Have you tried lots of practice? Took me a lot of laps to get from 3:23 to
3:20. I also dislike how the eagle (and lotus) feels at spa, even though
they're nice cars elsewhere, but they are the fastest. I did my PB in the
eagle with default setup (3:20.31).
It was only about a week ago I did that PB so I can tell you which corner I
had to improve to get the 3:20, maybe you're having problem in the same
corners.
The main problem I had was a right hander two turns after stavelot.
Stavelot is the sweeping right with barriers both sides about 2/3rds of the
way through the lap. It's followed by a slight left kink, and then theres a
bigger left kink which leads straight into the first of two right handers.
I detest these two right-handers, but anyway, I was taking the first one
*way* too slow. Instead of braking, as you come round the left hand kink
and see the turn just mostly release the throttle and get the car way over
to the far left hand edge of the road, then pull the car hard across to the
inside at the apex and you'll find you can take the corner a lot faster.
The next corner I improved at was blanchimont. After those two right hander
I just described theres a great massive straight, and then a kink to the
right. The next corner, a 2nd or 3rd gear left hander is blanchimont. You
don't need to brake half as much as you'd think here. Brake less, take the
corner faster, and 'throw' the car over to the inside as you take the turn,
and again you'll be able to take the turn quicker.
Other bits to work on, get a good exit from Les Combes, and try not to lose
any more speed than is necessary in Masta.
Anyway, I'm going to edit my version of Spa and remove Malmedy ;)