Well, the cut down worked out quite well, I'm vaping it on a 78mm manual right now. If you've got a Dremel it'll be much easier to do than using a hacksaw and files. I used a Dremel and cut the carto down to 11/16" overall length using a cutoff wheel. I used a grinding stone to "even" out the cut and take the burrs off the outside. I used a milling tip to clean up the burrs on the inside. I pulled the inner air tube and am using the little drip style tip that comes with a CE3. I flushed it out, thoroughly, to get the metal flakes out, dry burned a little, and it works like a champ. Two drops at a time work great! Total time, under ten minutes.
I'm inspired, I'm gonna give this a shot soon. It sounds like it would work much better than a full-length carto. At the very least, it'll be something to use until I get a 901 atty