Not quite sure what to say given that every extension I can think of is cheeky. You’ll have to use your own judgement.
That bit Hindle Pie shows is the classic Cumberland Clough cheeky descent.
It’s techy and great. Not many walkers on it either.
39 seconds in this video is one of 2 techy bits (in bivvy mode).
[video]http://www.youtube.com/watch?v=0ZqZtHnTyO8[/video]
This is the full descent from 6:15 in this video (in downhill mode)
[video]http://www.youtube.com/watch?v=vV6NisQuaAY[/video]
In terms of lengthening the first ride.
Plenty of options into the Goyt Valley. That would add a biggish descent and biggish climb.
If you like technical descents, then Stakeside is a cracker.
If you prefer something smoother, then the switchbacks down to Errwood Hall are good too.
You can cut across straight from the top of the Derbyshire Bridge/Buxton Roman Road to drop straight into the top of 3 Shires. A lot of the descent is double-track though.
There’s absolutely tons of stuff, but as mentioned – mostly cheeky.