OP
Thank you for all of your advice. Based on your comments, I intend to order the 104's in the near future.
I will keep the 120's because I may still want to dive singles on shallower dives, when shore diving or when working with students. Besides, I'll still have the Pioneer wing, so it seems silly to give up the tanks.
I will keep the 120's because I may still want to dive singles on shallower dives, when shore diving or when working with students. Besides, I'll still have the Pioneer wing, so it seems silly to give up the tanks.