How To Approach Slides Mid-solo?

Hey all,

I'm currently slowly tackling the Symphony of Destruction lesson, which has one of Marty Friedman's lightning solos in it, still only up to about half the pace on the solo at this stage!

I don't think I'll struggle too badly building up my speed along the bends, arepggios, hammer-ons and pull offs, but Im struggling with the high tempo slides in the middle of the solo.

The slides are executed over 7 or 8 frets in some cases, and only done with the fingers, no glass/metal slide is used. The problem I'm seeing, even at low bpms, is consistantly nailing the distance of the slide when way up the neck.

When sliding from e.g 14th fret to 21st fret (using little finger), even at low tempos, i'm only landing on the 21st fret 75% of the time. When under/over shooting it, its' very audible to the point it ruins the solo for me.

Anyone got any tips for nailing the right note every time?

Fast fret/new strings/solid calluses on fingertips/slow it down more/build up the pinky finger strength?????

Any help appreciated!