can i uses this for my steel 40 ? also because it goes on your bcd, will it work if mine only has 1 strap ?
Yes it will work on a 40. On a 40 steel I would use bth straps
I would not recommend that configuration for two reasons. A 40cf cylinder would not be stable on a single strap BCD. And, a cylinder that size would definitely have a turtle effect. I suggest slinging it.
40 cu ft won't work. Personally I wouldn't even mount a 30cu as a pony if you only have 1 tank band. These mounts are awesome for the intended purpose of holding up to a 30cu ft pony with 2 bands. Those tanks are long and heavy and with only a single point of contact (which is not in a cradle like your primary tank against the bcd backplate) they will twist and turn on you as you swim. I use a 13cu ft with one band -no problem, but that is substantially smaller and lighter. I always use 2 bands if hauling a 19cu ft tank - I'm using a Zeagle Ranger BCD and I think these bands are awesome. Easy to swap tanks etc.
This item works great, but since it mounts to the BCD straps I would look at a different option, I tried it with 1 strap and it does not keep the bottle stable.
It works great with a smaller bottle and two straps. I would not recommend it with such a large bottle and only 1 strap. I don't know how stable you would be with it.
You really need a 2 strap BC for it to be secure. You could alsosecure one of the straps with a short bolt if you have a space. I love this item and bought several. I have them mounted on the back of my twin tank set ups too.