I'm not a particularly good altissimo player myself but my advice is this:
1. Learn to play the notes you can already play REALLY WELL (this is the first part of Rascher's approach to altissimo in "Top Tones", although most choose to ignore it.)
2. Learn the harmonic series so that you "pre-hear" the series of overtones you are trying to play accurately when you are working from the fundamentals.
There is a lot of info archived on this forum about altissimo and some of it is very good. Read it and use your intelligence to decide what is relevant to you. All the best.
1. Learn to play the notes you can already play REALLY WELL (this is the first part of Rascher's approach to altissimo in "Top Tones", although most choose to ignore it.)
2. Learn the harmonic series so that you "pre-hear" the series of overtones you are trying to play accurately when you are working from the fundamentals.
There is a lot of info archived on this forum about altissimo and some of it is very good. Read it and use your intelligence to decide what is relevant to you. All the best.