For the spring rates, I think a 4K/4K setup (providing very slight oversteer) should be a good compromise for everyone on the list.
Regarding the choice of springs, I'm working out the numbers just now and, provided everyone on the list (5 so far) is confirmed (i.e pay their deposits when the time comes), I could possibly upgrade everyone to the Swift springs for not too much over the original quoted price (probably around $200 or thereabouts). At this price, it really does become a no-brainer tbh (especially when you consider the Swift Springs retail for $400/set)