I've tried those. Dangerous Waters won't even see them to import them.
The only thing I've been able to do so far is take one mission from 688I, import it into Sub Command (that crashes to desktop for some reason 9 times out of 10 the second I import a 688i Hunterkiller mission), edit it in there, save it, then import THAT file into Dangerous Waters where it needs MORE editing. What a pain.