Thanks to everyone for your thoughts and ideas.
The carpet tape is a good idea and I just happen to have a roll. I agree that while my example is a nice piece of wood it does clash a bit with the body. I do have a huge piece of claro walnut too, but I'm thinking that on this bass either purple heart or ebony would have the right contrast.
As David and Dave have implied, this will give me more flexability over tonal quality. Plus it's a little more comfortable than the corner of the pickup cover.
In this incarnation, I think it may be putting my thumb a bit too far away from the strings, especially the C string... so I'm making a slimmed down version from purple heart. I'll post back in a few days with the results.
- SoM