I have the need for a number of quick make shelves that look good for
holding light objects for display in teenager's rooms, and (they) want clean
looking floating shelves

here is my 2nd thought on making them

3/4 " stock, atleast 19" long, and 6" to 10" deep
drill or bore 1/4" holes quite deep.
use steel rods in the holes to give deep support
The holes would be set whatever distance apart the stud centres seem to be.

Questions:
does this seem reasonable?
how deep do you think the holes should be
- in the shelves ? 1/2 way through is what I'm thinking
- in the wall ? 2" into the stud
- use polyurethane glue on the rods in wall, nothing in the boards


I have a drill press, and a jig to hold a board on edge.
I would need to get a long bit.

Thanks in advance

Matt