FWIW, standard 1/8 endmills tend to be a bit long in the flute for slotting with. Stub length is about right for heavy duty use.
If you have the know-how and a grinder, it is possible to shorten a standard endmill, and regrind the end flutes so it will center cut. I typically only try this offhand with a 2 flute, because there is not enough room to work around the end of a 4 flute as easily. I recommend a good CBN wheel with a sharp edge reserved for this type of work, as it will grind a lot of tools and still maintain that sharp corner for a very long time.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)