RE: "In a hard grounding, an external bolt on keel can be forced through the canoe body and hole a boat."
An external lead keel on a properly constructed solid glass hull will take a lot of abuse with no material damage. E.g. this hauling we found a half inch deep, foot long gouge in the bottom of our external lead keel, due to bouncing over a rock in a five foot seaway. If this keel was encapsulated, any sheating would have been removed and we''d face the subsequent risks described elsewhere. As it is, after a half hour with a grinder and some epoxy filler, and we''re ready to paint, no worse for wear.
This keel is mounted on a heavily reinforced solid glass stub connected to a grid system. The keel could not be driven through this mounting area. Abuse adequate to break the framing and drive the keel with the entire reinforced stub area through the surrounding hull would probably also be adequate to similarly destroy an ecapsulated keel. (More severe grounding could damage the grid system which can be expensive to repair...)
I have seen external keel impacts damage the surrounding hull laminate in several cored hulls, so I offer my comments only regarding solid glass hulls.
I think the design question of an encapsulated keel is in fact similar to that of cored hulls, recognizing there a re different schools of thought for both subjects. Beautiful boats can be designed and properly constructed with encapsulated keels or cored hulls, and give their fortunate owners many years of excellent service. However, should these boats experience not unusual impacts, the owners hmay have material problems to deal with, which would not occur with alternate forms of construction.
So what my thinking comes to, with the unavoidable risks inherent in boating, why include any big ones that can easily be avoided? Sort of like choosing gas versus diesel, although the market has spoken on that choice. Just my point of view.
(Those Hood designs are beautiful boats, and well worth bending opinions and points of view to consider...)