Your time off won't be regular enough to commit to a day a week. You'll be there one week, miss the next two, be home for the next two, miss three, etc, etc. As others have pointed out though, you don't 'own' your flying hours and as a S/O you'll often be close to max duty and/or stick hours a lot of the time meaning that your ability to pick and choose days to fly will be significantly reduced.
If you're in QF then about the only hope for other forms of instructing is going to be with some defence leave and the RAAF or AAFC.