I've also welded in many floor pans.. Here's a reason I wouldn't want to rely on glued in panels, if you're involved in a collision in a unibody car do you really think a glued in panel at your feet and legs will stay in place? I sure wouldn't want a floor panel pop loose during a collision, it would be like a giant razor blade buzzing around at your feet and legs cutting everything it touches. Being in a car crash is bad enough, now you multiply the danger with sharp edged steel cutting your feet off, not for me. Weld those floors in place.