I would like to have Package Tare: Small to Medium: Added Percentage:Weight to calculate. Is there some switch or piece of code that prevents it from calculating? I am on ZC 1.5.4 and Tare won't work in neither my custom storefront nor Classic.

I have run offline Excel simulations using product weight and preferred percentage:weight settings, and the results would be perfect if I could only get Zen Cart to calculate Tare.

Please advise.