Hi Rob,
Suggest you try the MFC 29cm first, that should be more than big enough for your weight of 70kg.
Re the max sail sail size - as you say "ideal" can vary on sail type/personal choice a lot - but at 70kg, I would imagine around 6.2/6.3 in a powerful sail, working well for the 95 for you as the max size. Ideal size between 5.3/5.7 due to your lighter weight.
But of course you can always give the 7.1 a go on the 95, we used to test those with 6.9 Disco/Duke sails in the past and it's the limit but works. You may need then to use the 32 K4 in case of too much pressure on the rail!