I had a feeling you were going to say that, hence my question.

Yes, you definitely need the top mount ferrules. They're smaller, use a much smaller hole and their edge is designed to take the string safely. If you tried to use a rear mounts on the top you'd not only have the unecessarily oversized ferrules ruining the looks of the guitar but their edge would probably instantly cut your strings under tension. They're just not designed to be used on top.