The figure G thing is a very good point actually. I didn't think of that. I'll consult my soloist first (she is a VERY good saxophonist), but I may well change that.
To be honest, the entire cadenza passage is a bit "tacked on"! I wasn't sure what to do, so I just put the words "ad lib. cadenza"...mainly to make the soloist squirm, because I'm harsh like that (and, after working my way through some classical cello concertos, I feel that the improvised cadenza is something of a lost art). But I do see what you mean about the high A. I'll put in some impressive sounding arpeggios to lead up to it or something.
As for the bizzarre time signature: the main reason it's like that is because of phrasing really. The beat is felt as 4+3, 2+2+2. Using 2/4 and 5/8 might just make things even more complicated, although I do admit that writing everything in quavers (making the time signaures 7/8 and 6/8) would make it more readable. Besides, I've become desensitized to confusing time sigs after playing The Rite of Spring
Again, thanks for all your comments.