Finish for table top support and slider

I am building a dining room table (bubinga and curly maple). The table
top is supported by dovetailed extension sliders and some "joist" cross
rails. Usually I finish all surfaces on my projects, but looking at our
current dining room table there does not appear to be any finish on the
under supports. I was originally going to simply wax the mating
surfaces of the slider and oil the rest of the surfaces. Now I'm
wondering if would make sense to simply wax the entire under structure
and not bother with a finish. What do the experts out there recommend
doing? Incidentally, the curly maple legs/tressle will be oiled and the
bubinga top will get a poly gell for a hard surface.

Thanks, Bob