BBQ said
The material I have now has a small sett (5 7/8" and 6"). This makes for what seems to me a rather shallow pleat,
That's actually a pretty typical sett for 11-12 oz wool tartan. You have to get up into the 14-16 oz range before most tartans have bigger setts (unless you have a tartan with an ABAC- or ABCD-type repeat, like the Black Watch family of tartans). Most kilts that dancers wear have setts that are 6" or smaller, and they swing just fine. So, deep pleats are nice but a well-made kilt will swing just fine even if the pleats aren't super deep. The pic below shows a kilt with a 6" sett - it has pretty nice swing even though the pleats are less than 3" deep.

Barb