Over Unders or Threshold

Ive found O/Us hard but the 8 minute threshold at 108% of threshold nearly impossible. If O/Us are known as the toughest workouts, how on earth do you manage 8 minutes at 108% of threshold. Im convinced I have a different FTP for SS workouts that above threshold stuff or maybe i’m just more suited to them but should I lower my FTP for these workouts??