JoelW:When I carry my 30cf I keep my right side weights 2# heavier than the left side and that seems to balance the bottle under my left arm. If I don't, when I am just floating I get a slow roll to the left.
JoelW
That's basically what I do, except my 30c.f. sling is on my right, and I use a two pound clip-on on my left side. Works fine, no foul ups. My friend puts his on the main tank, but I have not seen any difficulties. Whatever makes you happy.