These were the original spacers 3.5mm each (i.e. 17.5 for 5) on the inside of the spider to space out the large drive sprocket (54T) and the index or timing chainring mounted on the outside of the spider.
This would improve the chain line and make adjusting the front derailleur easier as it was at its limit of inboard adjustment.

First I tried 1mm first but it caught as the gears were changed back to large ring.



I then tried 2mm and although it caught on the wider "quick-link" it seemed otherwise fine.
The second shot shows it just catching on the "quick-link"



I removed the quick-link and joined the chain.

We rode to lakes entrance the next day Wednesday where the chain suddenly snapped so we had to scooter home.