Why do not need to lose as much as possible? I don't want to be negative but that sounds like you are setting yourself up for failure as 1 stone and a half may be an unrealistic target .
In 7 weeks on any plan you might hope for between 7 and 14lbs. And will red days give you better losses? Who knows! Some people like red days but if you are not a great meat eater then you may struggle to stay on the plan, so losses are not the only thing you should consider.
If I were you I would just aim to stay on plan 100% between now and your holiday, on whichever plan you normally do. Then you are setting yourself up to succeed and not just until your holiday.
