Actually, the op (me) was not asking how to goop it up but rather suggesting a new way (at least to me) of replacing a plywood
knee with solid fibreglass.
But this afternoon, I drilled some of the holes, in the worst knees, deeper. I was absolutely delighted when dry-as-a-bone (don't know why they say that because bones are not dry) sawdust was extracted from very deep (laterally) within the knee. Last winter that same hole was quite moist. The worst of the knees was still damp when drilled deeper but that is a running backstay knee.
The backstay knee is now the dampest and most concerning but I think that drilling laterally, into the inside edge and using CPES then filling with thickened epoxy, is the best option and is what I will do... I think