Well, I wouldn't say there is right and wrong here, after all, they are your heads, you can shape or sharpen them how ever you wish.
I like to hold the original shape when sharpening.I learned, that if I keep the exact same angle from end to end, the blades get sharp and hold the tanto tip integrity. Its easy to get a little inconsistent at either end, so its a little tricky by hand. I use a file, and strop. All you need to really do, is raise a good bur on the blade across the entire edge. Then alternate sides staying true with bevel and the flat, increasingly ever so light pressure, until the bur is so thin, the file cuts it off when it comes to such a fine peak that it forms a true edge. With a good bur, you can often see it lift off, as it looks like a shiny hair. Anyway, to keep the true tanto, just follow the original bevel end to end with equal pressure, its that easy. This head needs a little more work and shine, but its shaving off hair easily as it is with nothing more then the file. Note the tanto has kept its full original shape.
The tanto, is suppose to be one of the most stabil/tough tip designs...I dont worry about sharpening the very tip edges of the tanto, and leave them to chisel.