Thanks. My own “legion” now has a unit that has 50% slingers.
After I made the figures it struck me that any slinger legionaries actually deployed may well have operated in pairs a bit like skirmishers of later periods. One observing and shooting (scutum slung or on the ground) and one protecting with his shield (or both shields?) and with both soldiers pila. Why I did not think of it before as all through my military training the idea of supports while moving was emphasised.
Sometime I may make another unit of “pairs”.