Different agencies (& other interested organisations) have different times, OTTOMH BSAC allow you to fly after 6 hours. Have a read of some of the papers here:
The Rubicon Foundation: FAD Tables
From memory, the issue is to do with tiredness & dehydration, so long as you recover from both you should be fine.
Frankly, suck it and see is about all you can do. Personally I wouldn't worry about diving on Sat after a flight on Fri, just make sure you drink lots on Fri night (& I don't mean alcohol!). With regard to the Mon flight, I would leave as much time as possible, use nitrox for the actual dives & if I was feeling very worried about it, spend half an hour or so breathing pure oxygen after the Sunday dive.
hth,
cheers,
Paul