Syncing new midi tracks to sped up audio mix (Cubase 10 pro)

I have an old project created a long time ago in Cubase 6. It’s too awkward to try to work with the old project file and the mix sounds pretty good but for two things:

  1. The tempo drags, I would like to hear it about 10 bpm faster
  2. I wish to ad some midi tracks with the amazing new virtual instruments I’ve acquired
    I’ve been doing this successfully with other tracks that don’t need the tempo adjusted, by dragging the mix into an empty audio track and using that as a reference. If I’m not sure of the original tempo it’s not hard to tweak the tempo (it was all recorded to a click ) so that the audio sits right and away I go happily adding acoustic guitars, mandolin, pedal steel even, No sweat,
    On my problem track I use Audio-Advanced-Set Definition from tempo on the imported mix. Now there’s no problem now adjusting the track 10, even 20 beats faster without changing pitch and audio quality, Good trick.
    Alas the audio track doesn’t sit right against the timeline. It has a nice clean snare crack on 2 and 4 but it is way off, so theres no way to sync new midi events to it.
    There must be a way to do this. Does anyone have an explanation?