Always, always, dig the soft coring out around any hole and fill with a thickened epoxy, top side or bottom side:
* To create a solid incompressible wall to prevent the loss of clamp load from the fasteners.
* To seal and protect the core from ingression that can lead to saturation and delamination.
* To unify the structure should you ever decide to replace or re-bed the hardware in the future.
* Reduces the dependency on the sealant selected to the structural soundness of the job.
Cal 9.2 #19 SilverSwan