USPS First Class Shipping Should Not Be Available If Volume Exceeds A Certain Amount
I've had a couple of occasions in which print requests when packaged has come out over the USPS FC limitation of 13oz or 368 grams. My current process is to check if any amount over 300 grams is used before changing the shipping option on the order before payment.
It would be a nicer customer experience (and easier on the Hubs) if shipping options that have weight limits not be available to the customer if the projected printed volume would exceed an estimated weight in the material being chosen. Since you're already able to calculate volume, you should be able to calculate the weight of needed.
Bo Herrmannsen commented
tried to send an email to: firstname.lastname@example.org ?
Michael Zhu commented
Just a note, this doesn't have to be specific to the US. I understand there's other regions with their postal services having different requirements. The USPS FC example I give is just for the US.