Of course it depends on how your hair grows but I've been shaving with a straight almost 3 years now and I still can't get as close on my neck as the rest. I've tried all kinds of crazy angles and its still not the same. I've figured out that the only way is to shave E-W and that is impossible with a normal straight without cutting my throat. Maybe someone with a huge neck can do it but I can't. I do have a tradition Japaneese straight and because it has a very short blade I can do it with that but that razor has other limitations of its own.

I've just accepted the fact that the shave on the neck will not be quite as close as the rest. Maybe others will chime in with some secret formula for success.