Well, were driftin away from the topic (my fault)...
However, in our 680 left and right boxes disagree (have been told by Honeywell that this is normal), VS varies - a lot - if you are using VNAV. We have tried any setting between 2,5 and 4,0 that would give us an aeroplane not oscillating.
Your scenario would only work (on our aeroplane) if one used it as a guidance only. (VS mode then) Have been on a Honeywell workshop and all crews there had the same experience as I had.
The aeroplane I flew before had the Proline 21 installed and the VNAV capability in terms of precision and annunciaton where amazing compared to what we have now. (and that aeroplane had no autothrottles too - which Honeywell pretends to be the issue of the Sovereign, why it would not work as good as it does apparently on the Falcons and Gulfs)
On the UK stay up thing, Iīve tried that into London (often in City and Farnborough), into Manchester and Brum. Wonīt work or the just donīt give it to bloody Krauts. AGP? far too nice a destination, not allowed to, my peers go to the East a lot (where you mostly can plan youīre descent freely and then the old rule of thumb works great even in the Sov)...so I canīt try it soon.
However, the nice thing is the Sov can descent like a brick if necessary. Makes up for the avionics...