So the automatic rate calculator provided by the Postal Service for shipping, that promised to be rather hands off and easy, has instead turned out to be cumbersome and rather off the mark - requiring me to go back afterwords and adjust the shipping so you didn't pay too much.
To try to streamline the whole process from the get go I've set up some new rates in the checkout (for inside the US only - the calculator gets it right for international shipments).
The new rates are the prices for USPS flat rate envelopes and boxes. The prices are: $5.00 for the first $30.00 and $9.00 after that. The first rate is for a flat rate envelope, which will really only fit some fabric or 1 book. But most anything will fit into the $9.00 flat rate box.
The rate calculator will still be available as well, so during checkout you find that Parcel Post is cheaper than the table rate, by all means use that.
I hope that this solution will be cheaper and easier for everyone. And although I'm pretty sure I've got everyone, if you ordered recently and paid more than $9.00 for shipping and didn't receive a refund please email me and I'll correct it!