Guess I still answer you about the significance of matching XJO and SPI then.
Depends how it closes is the main thing.
Last time it closed close to par it was an outlier from the norm of significant discounts and produced a sharp move down.
As a general principle, that is the way to approach it.
If it doesn't then I see if we start to build a new normal and look a the medium term.
It can seem a little confusing and is why I suggest you need to look at SPI/XJO relationships over the history of the SPI. Once you do it is fairly obvious how it all works.
There are only a couple of principles really. One is the outlier effect and the other is when it is normal for premiums and discounts and what do they say about the trend.