I'm sorry, but...
Wouldn't 25 miles to touchdowb give you something around 8000 feet to lose?
The acft descends 1000ft for every 3nm, right?
1k....3nm
Xk...25nm
X = 25 / 3 = aprox 8k.
As in your example the acft had to reduce 20kt to the flaps up speed, we would have something around 23nm to descend. Thus, 7500ft would be the right figure in my opinion!
But this is a slick bird, its always a good policy to have 1 or 2 extra miles in ur pocket in case you face some tailwinds.