A collection of posts by David Weber containing background information for his stories, collected and generously made available Joe Buckley.
You cannot fit a Warshawski sail into any missile. This question has come up several times now. It is impossible to build a Warshaski sail missile at all, which is why missiles cannot be used in a grav wave in hyper.
Any missile with any impeller drive is much larger than the final target bus of even a Ghost Rider MDM. Counter-missiles are smaller than shipkillers; they are not tiny.
I hope this isn't going to become another grav lance! :-)