USD 40cf Buoyancy Characteristics?

[Ghetto Diver]

Can anyone shed light on how they trim?
Early steel PST tanks, the ones used for triples in the 50's (2250/40cf)

I searched and found nothing.
Some of the photos I have seen of the triples in use seem they seem tail light.

 

[jvanostrand]

I got some information from:

Vintage scuba tank [Archive] - Spearboard.com - The World's Largest Spearfishing Diving Boating Social Media Forum
And https://www.scubaboard.com/communit...20-20-20-202017-01-24_zpsllikkprt-jpg.404671/

 

[Ghetto Diver]

Thanks, but not seeing specifics.