I don't think any kind of adhesive or tape will be strong enough to hold up to the abuse that a trackball might take. What I would suggest you do is find some countersunk screws with small heads and try to screw down the plate as tight as possible. With some luck the screws should sit flush with the plate. If not, bust out a dremel or something similar and try to smooth it out. If not, you can try and rout the hole for the plate out a bit deeper, then screw it down as tight as you can, and bondo over it. Sand the surface nice and smooth, and make sure the hole for the trackball stays intact. Just a couple of ideas, let me know if you need some more help.