Not including volume...

[Mr. Bubble]

Oh yeah, I ran across another rule of thumb I wanted to mention. Use the volume of your tank to match the depth of your diving. i.e. 80ft or less diving, use an 80cf tank. 100ft use 100cf tank, 120 use 120. 130 is max recreational so if you dive to the limits all the time a 130 is for you. plus or minus, just a good rule of thumb.

Mr. B

 

[ACR]

Weight and length as it relates to trim. Are you a taller or stouter person?

If they are all new then they will be 3442 PSI and be DIN/yoke capable. If you are looking at any 3500 PSI used cylinders those would be DIN only.

I'm fairly tall, 6'3" about 205lbs and in relatively good shape. I'm not too concerned about the relative weights though maybe I will be if I end up doing a lot of lugging. All of my diving for the foreseeable future is within rec limits.

I'm currently an air hog, so my limiting factor at the moment is my gas volume. The extra volume will be nice but my SAC will likely (hopefully) get better in time which is why I'm hesitant to just go with the biggest tank I can find.

I may double up sometime in the future so weight may start to become a consideration, but at that time I'll probably have a larger selection of tanks too