I look at solo as having a skillset that does not rely on a buddy that will statistically fail me. I always assume that I am diving solo with another. Arrrogant perhaps but unless you are diving with a regular buddy you dont know who your getting wet with. In the military I would relate this to picking a hooker based on her shot card being up to date. I seldom take a pony with me but that is dive dependant. For a pony i use a al40. Small ones just dont hack it. OOA at 100 ft. high stress related respiration rate and that is the up side. Now do this with a insta buddy with 10 dives logged diving beyond thier means and training. Add to that rough water and you will drain a 40 in no time. If youare going to do solo then it is possible that tech in in your future and the 40 is the size to use and clips to your bp/w easily without changing your trim.