I've been experimenting with the CS for little bit now and just recently added the flat rate options. I only have CS enabled for some of my listings, and the weights and measurements are accurate.
I use regional rate A boxes quite often so I added that as one of my package preferences today and went to test if it worked. It seems that regional rate is overriding the flat rate padded option.
Hers is a link to the product I'm testing:
https://www.etsy.com/listing/62707472/liquid-resin-luxe-doming-epoxy-resinThis product fits into a flat rate padded mailer, and weighs 26.5 ounces.
Tested to zip codes 85379 and 23455 (AZ and VA, shipping from AZ)
If I have Regional rate turned off it will charge $6.10
When I add the regional rate A box it tries to charge $10.72 for both locations.
I was under the impression it would charge the cheapest amount available to the customer. Any help would be appreciated!