Hello Jonathan
I am amazed that your screws came out whole, well done . I would guess then that we have a problem with electrolytic corrosion due to some neglect of the keel ram anode. I did find two bolts in the keel recess, all that remained of an earlier anode so at some time in the boat's past the anode has been allowed to totally disintegrate. At that time maybe the corrosion occurred. I would like to get hold of the keel drawings is possible, if anyone knows where they might be, I don't suppose Parkers cast their own keels .
If you still have the original book of instructions for the boat you may see some lines on the keel drawing suggesting that there are three straps each side in the lead where the screws are tapped in . I am not so sure that there is not one continuous part each side as I failed to miss steel with any of my drillings for the extra screws, that was quite a hard two days.
Jan Newman
325/32
Blue Moon