Lalalamort I feel like I have to add a bit of my personal advice here as I think you are being led down the wrong path by a particular person here with more opinions on things than I have had hot dinners.
I am also 75 kg's and have been sailing for over 25 years. I had only had pre millenium sails and boards up until about 18 months ago. The difference between the older boards such as yours and the newer boards is a massive amount.The same goes for the sails, even moreso! The wind range you can now take modern sails out in is pretty incredible. Although I would love to see you try and hold that 7.0m in more than 25 knots
By that kind of wind strength I'm down to my 5.0m and fully powered up. And also the quickness with how modern boards can get up and plane compared to oldies is also monumental. Do not for one minute think that a newer board such as the JP you rode or the North sail are in any way close to what you have had in the past. For your weight I would NEVER recommend a board of the volume being mooted about on here. My all day every day board is a Fanatic Falcon slalom of 90 litres and in 12 knots I am planing with a 6.7m race sail.
Please, go back to Wind Surf and Snow and speak with the guys there. Get them to show you how to rig your gear right and I am sure you will be amazed at the difference in performance. New gear is very sensitive to correct setup and can be the difference between planing and having fun or slogging and cursing the people around you going faster. Don't put a modern sail on an old mast, it won't work.
I wouldn't want to see you on a modern board of anymore volume than 105-110 litres considering your weight and I think a 6.5 to 7.0m sail will be fine for most Sydney conditions.
I stress this is only MY opinion but please, go and listen to some experts. That's what the shop is there for.
Good sailing mate
