15% seems a little high for interior use, but you will probably be ok since you are not joining the slab to anything other than a steel rod. I think ideally you want it between 6% and 9% for interior use. How long have you had it inside your house? Have you given it a month or 2 inside your house to acclimate and see if it will move any?
You might consider resawing it into thick (~1/16 - 1/8") veneer, making a torsion box for the shelf (plywood or MDF), and applying the pecan to the torsion box. This would give you the same/similar look, it would likely be lighter, and wood movement would likely be a non-issue.
You might consider resawing it into thick (~1/16 - 1/8") veneer, making a torsion box for the shelf (plywood or MDF), and applying the pecan to the torsion box. This would give you the same/similar look, it would likely be lighter, and wood movement would likely be a non-issue.
