[LAD] non-sequencer tempo drift

I've been playing with Non-sequencer over the last few days, love the simplicity and uncluttered approach to the programme, however I'm finding if run alongside Hydrogen or Ardour, the tempo drifts out of sync, this occurs playing any song  longer than a couple of patterns. The obvious answer to this is to have ardour as jack transport master, Non-sequencer does not like this however and crashes. I post the question here rather than Linux Audio Users because I plan to write applications utilising Jack MIDI myself and am wondering the best approach to implement tempo in absence of alsa sequencer, which I found quite nice to use but still jittery even with high res timers / real time kernels.