Thanks for the info! I've now applied the rule (I think!) to all my listings. For some reason, 6 didn't "take" - I don't know what was different about them.

I'm worried it didn't, for this reason: while most of my listings were already at $1.50 postage, a few were $1.30. After applying the rule, they were still $1.30 (I would have thought they'd change to $1.50). Maybe I didn't give it time to update? ( I've now manually changed those to $1.50.)

Anyway, do you know of any way I can check if it worked? - Short of waiting for someone to buy multiple items and then seeing if their invoice automatically calculates the correct postage.