The 6 cf bailout system is always, but barely negative, so as stated earlier you just don't notice it. And it clips behind the wing so you don't really feel it either.
As far as gas quantity, that's every individuals choice. Some divers don't mind carrying large pony tanks, so they're happy with bigger ones. Many hate wearing bulky ponies, so this 6 cf model will be one they will wear instead of going without.
I wear it most along with my 30 cf deco stage, so it's nice to know I could use it to get me up to about 30' and then switch to the larger volume deco gas.
Just for grins I did a couple tests.
The 6 cu ft tank used in my pool at 6 ft depth and it lasted for 13 minutes, very relaxed and warm. My SAC was 3.9 cfm. (Your mileage may vary, YMMV.)
The same tank lasted 4.8 minutes at a fast swim pace where I swam 770 ft at 4 ft. of depth, with no push-offs from the walls. SAC of 1.1 cfm. (YMMV) This was an estimate of the speed I might use if needing to get up from a deep dive to the depth where I could use my stage deco tank, approx. 30 ft. If you do the math you will see that the tank would have allowed a theoretical horizontal swim of 192 ft at 115 fsw.
For me this is a lot of emergency gas to get up with.
There is a handy pony tank guide program on the bottom of Spearfishing Magazine's home page
www.spearfishingmagazine.com. It let's you run all the math... and it agrees with my #s above.
Chad
