Hi knowledge base. Just bought an old windsurfer one design but Bombora version. I also have a Red Paddle wind/SUP which I never used for windsurfing until now. It is ready to hit the water.
I used to mainly surf and slalom boards back in the day (80's early 90's). I was 75 - 80kg.
I used to plain easily on my custom 9' wave boards with a 5.2 or 5.5 Pryde sail.
Now when I look up tables for sail size and wind strengths it says I should have a 7m, plus now I am 95+kg I should have a 9m.
I didn't even think about this aspect before deciding to have another go at it.
I am happy to plod along for a while but would like to get back on to a faster 9ft ish board sometime.
I have 3 standard Windsurf sails and an old cambered 6m.
Am I really going to need a 9m? (allowing for extra kgs) and why is that if my old 5.5m got me planing.
Also can I cut a 460 fiberglass mast down to 430? Should I reinforce the bottom?
Plus it seems there isn't anywhere in Sydney south to buy parts or am I wrong?
cheers Thanks for listening and thanks in advance for any info.

Do it.

Adding to what Subsonic said, the bigger sails also grew out of better (read: shorter/wider) short boards for lighter winds which made planing in lighter winds much easier. Changes in both sail and mast tech means the big sails are lighter and have a bigger wind range so you aren't way overpowered when the wind comes up. They aren't required by any means but certainly help when sitting on the beach on a light day and you have that "if there was only a bit more wind" feeling.

If you live in a place with deep enough water, you may eventually want to look at a hydrofoil as their efficiency means that instead of getting a bigger sail, you can use a smaller sail and foil. You don't need to be an expert or even advanced to foil. We've had folks who instead of going down the short board/harness/straps path just went foiling instead since straps and harness can be optional.

I wouldn't fool around too much with the epoxy masts. You can generally find used standard diameter carbon fiber masts (SDM) quite inexpensively. They are much lighter and user friendly. Most smaller sails now are designed around reduced diameter masts (RDM) which are typically more robust and easier to handle but often not as cheap used. However, going forward, these would be more compatible with any newer gear that you might decide to use. Modern sails can be somewhat sensitive to mast bend and stiffness and as a general guideline, I'd suggest you stick to the recommended mast length.

Welcome back - it really is as much fun as you remember, perhaps even more so. While most of us aren't as light as we were in our youth, most boards in a given wind range are wider than they were back in the day which means they are much more stable even if they are shorter than what you rode back then. The 9 footer (280ish x 59cm) is now 235-45 cm and as much as 75-95 cm wide (depending on intended use and wind range). But whatever you decide to ride, it'll be fun.

Let us know how it goes and good luck.

Get a lesson/demo on the newer windsurfing equipment and foiling equipment too, and go from there. And yes, windfoiling is a game changer, I now can get up in 12 knots with a 4.5 wave sail and a higher aspect wing AFS F1080 cm2, I weight 86 kg.

Thanks for all the replies.
RichardG. Yes that is the one. Amazed you found that. I have the proper mylar 5.7 (I think). The other two smaller sails not sure. Made by local sailmakers.
Mast base Bombora fitting missing but previous owner did a work around.

Sandman. I am trying to learn wing foiling but very slow progress.

BSN101. Have been thinking of ditching the wing foil and buying the LT. Clubs at Botany Bay and Rodd Point. End of season.

I couldn't help noticing when trying to wing foil how fast sailboards and kites are compared to wingers. That is what caught my attention for windsurfing again. Wish I had photos of my old gear. I seem to have photos of SUP's and surfboards but nothing for windsurf.

Thanks guys