For 1/8" Alum you are right on the border. So it comes down more to duty cycle. For light use you could get by with a 9 but for more heavy use I would go with a 17. You do lose a little capacity with the stubby kit, too. So keep that in mind. A 9 will be a little smaller than a 17 with the stubby kit, but not by much. Everlast is also a CK Worldwide dealer, so they can sell you a plug and play setup with their superflex hose and the torch of your choice. The superflex makes all the difference. Also before opting for a flex head, have a look at the flex-loc system. While a little bulkier, it allows even more movement, and you can swap just the head portion so you can switch between 9 and 17 heads depending on what you are working on.
Long arc, short arc, heliarc and in-the-dark!