Yes, that pretty well sum's it up. Use an elite fighter/bomber classed as a seaman on CV's depending on your preference of FW or BW, and a good overall stat sailor classed as seaman on BB's. The best overall general seaman can be made from the old original 14,10,10,10,etc sailors. And yes, you only want/need to have ONE.
Regards,
Nik
EDIT: I reread your wording from the original post, and must add this. For CV use you can benefit from the boosted ability your pilots will recieve. The seaman will do the same for your BB crew as well, however eventually you will probably find that slot put to better use with an additional engineer or repairer on your BB. You dont NEED a seaman on either ship, but you may find it more helpfull on a CV if you want your pilots to remain competative.