Class Not Working

Hello. I love your plugin. However having an issue with the “class” field.
I have 2 options for paintings I sell online “Print Only (Unframed)” and “Framed”

……when it comes to shipping, I need to charge more for the “Framed” painting because its much heavier and larger item to ship.

I have a plugin that will change the flat shipping rate by the class… when I enter “framed” under the “class” field in your plugin – it doesn’t show as a class anywhere.

I hope I am describing this well. I need a way to adjust the shipping cost based on the selection a customer makes. Any recommendation or solution would be greatly appreciated. I want to buy the pro – but I need to get the class resolved, and/or find another way to calculate different shipping based on the selection.
Thank you!