I suppose that you are a virituos if you play that piece, and 4th and 5th fingers trilling should not be a problem
just because it's a problem doesn't mean that you're not a virtuoso. It's one of the technical walls you'll hit when learning it.Since the dude didn't answer my question, I'll just give him this. When the right hand is trilling the SAME two notes, I do 35. But if the right hand has the melody while trilling, I use 45
, but I insist, La campanella is for those who consider 4-5 thrills a childplay
You learn as you go.