Upgradability/future options on a LP steel 121

[teknitroxdiver]

The extra length of the LP121's a royal pain to carry by the valve. You have to bend your elbows to clear them off the ground, and after a while, it starts to kinda tire you out so then you have to cradle-carry them so that means one tank at a time.
From a mechanical point-of-view, the lower pressures are actually better for a lot of first stages if you use Genesis valves or are a valve snapper-open. This is as opposed to slowly opening the valve and pressurizing the regulator. This is easy to do with Thermo or Sherwood valves, but Genesis valves snap right open when you turn the knob and this can cause premature wear on first stage components.
One of my LP121's weighs 58 pounds with 3600psi in it. It's heavy, but that's as much gas as is in twinned aluminum 80s. There are guys who dive with twinned 121s, and there are guys with bad backs who used to dive with twinned 121s. Each year, one list gets bigger. Once you mess your back up from overtanking, it's a tough recovery. If you need twins, I love the twinned LP85s. Each tank weighs less than an aluminum 80 and can hold 115 cubic feet of gas. When you start needing more than 230 cubes of gas with deco bottles, maybe you need to start thinking rebreather.
They cost a mint even now, but try pricing back repairs.

Interesting. I used some Genesis valves recently on some rental 80s, and they took half a turn to start creeping gas in...very nice valves.

 

[JS1scuba]

One thing to be aware of is that HP 120s are very very long tanks. They're almost 3 full inches longer than Al80s. I'd *really* recommend that you consider the HP100's or LP108s or LP95s. They are really more than enough gas and they are nice manageable sizes.

I am 6'1" at 260. I use HP120s and LP 120s as rare as possible. Mostly I use the LP108s and LP85s all in DOUBLES ... That said I do use the 120s for dives where i need a lot of gas (275 - 350fsw) The 120s are long and take a bit of handling.

Cheers