11.0 meter S-2
When you describe ". . .a roughly 2'' section that seemed to have a void or had become delaminated.", is this a 2'' square area of the keel that sounded as nonlamination when tapped with a surveyor''s hammer? Or, is this a visual assumption? It is difficult to provide a valued assessment of potential problems without a more detailed description.
IMHO, if soundings indicated nonlamination, the proper method of determining causes of the delam would be to strip the bottom paint and take accurate moisture readings. High moisture content and/or visual evidence of osmotic blisters is a dead giveaway of an inferior gel coat layup during production. Peeling the gelcoat down to a solid substrate is necessary, followed by a long dryout period. Apply a quality epoxy barrier coat, fill/fair and prep for new bottom paint.
If this is a result of blisters, I don''t think that simply drilling, draining and filling with ejected epoxy would be a long-lasting remedy. Get written estimates on the repair and make an offer with the repairs factored in. Of course, your offer is contingent upon a favorable survey. Whether doing it youself, or contracting the job out, you should be able to proceed with confidence.