Spin,
Don't be too frugal with the epoxy or however you attach the keel. Any force that is exerted on your boat will eventually be exerted on the keel and it's attaching points. That means it has to be fairly strong. Not a whole lot of point in making it stronger than the rest of the baot's structure, but at least as strong is a good rule.
The choice between an 'in-hull' trunk and a 'through-hull' trunk sort of depends on how much weight is going to be a problem for your boat. If done correctly, the 'in-hull is just as strong as the 'through-hull'. If the keel is going to be detachable then the through-hull thingy might be more convenient. So, now you get to decide which to do...
- 'Doc