A spi from 1997 will probably be cut a lot fuller than a spi from 2012/13. there have been quite som development in those years
There was a generation shift about 2002 if I remember correctly. Around that year the Tornado class saw the introduction of much flatter spis shaped with more panels from the sailmaker "Gran Segel" in Sweden. The next years the other sailmakers played catch-up before the olympic games in 2004. The F18 class adopted the same, flatter, shapes.

If you can afford it, buy a nice used spi from 2010-2012 and I believe you will find it a completely different beast.

I would have checked what type of line is used for the tack line. Nylon will stretch a bit.

Nice windy conditions!

On new spis you will find a "luff line" inside the luff tape. This line is made of dynema and is used to pre-tension the luff of the spi. The function of the line is to make the spi fly better as winds increase by taking the loads in the luff. Spi cloth and luff tapes are much more stretchy than the luff line. Besides helping to keep the sail shape the luff line also helps with sail longevity.