Since I'm being such a pest about this I figure I should update my post. I figured out that if I clone a plant I can make my omsp invisible and I can interact with it, too. I gave my all my variants an alpha mask threshold of 0, changed the invisible variant's shading to phong alpha, and made sure the invisible dds file had a black alpha. Now, whether I needed to change the shader and/or alpha mask threshold, I don't know. But I did just in case. And I was able to add slots using Orangemittens tutorial. So, aside from the fact that I can't seem to place a microwave on my omsp (which I don't know how to fix), it works great! Problem solved!
