Actually, the displayed weight is not a big deal. The shipping cost going up when adding additional free shipping quantities after adding a non-Free Shipping item is what's troubling. Add a bottle of ink to the cart and check the shipping estimator then add a stencil and the Free Shipping option goes away as it should. Then increase the ink bottle quantity and refresh the estimator and the cost will climb as the quantity of the Free Shipping item climbs.

Thanks for the attribute advice. I'll get it done.