You don't need a whole bunch of lift with steel tanks. 35 pounds of lift or so will be plenty. Door handles work great for steel tanks but suck for al80's unless you are putting weight on the tanks. I really don't think you will find any one sidemount rig to do both.
Well, there's quite a few rigs that work well with aluminum tanks AND have greater than 35lbs lift...
The biggest issue with larger buoyancy capacity sidemount rigs is how/where the gas is distributed on the back.
Diamond/triangle shaped wings tend to 'beach ball' and raise the profile of the diver. Integrating a baffle system stops that, but also ultimately limits the lift.
Wings that use donut shaped bladders with buttplates tend to raise up the buttplates when inflated. This destroys cylinder trim. The bladder should NOT run under the buttplate.
The other problem with donut or horseshoe shaped wings is that they don't focus buoyancy at the diver's center of gravity... the lower back and hips... where cylinders are attached. This opposes natural diver trim. Bladders with significant wing buoyancy at the top of the wing can create a pendulum effect that drops your legs easily.
When BI dove the XDeep Stealth Tec, I found its triangle design gave intuitive diver trim, the bladder didn't 'beach ball' significantly... and it doesn't rely on a buttplate... making it equally suitable for aluminum or steel cylinders. And, of course, the lift is sufficient for virtually any dive or realistic number of cylinders.
---------- Post added November 6th, 2015 at 01:38 PM ----------
The LTZ has 35lbs of lift (+ another 10 from optional duel bladder) so potentially 45lbs of lift.
Redundant bladders don't exist to provide supplementary lift. Not ever... Tec #101
---------- Post added November 6th, 2015 at 01:47 PM ----------
Luxfer 80's are 32lbs and need 4.4lbs of lead to sink that you have to carry on a belt....
4.4lbs is the positive buoyancy of the cylinder, when EMPTY. We don't dive the cylinders to empty, right?
... and that's the cylinder w/valve. But we put a regulator onto each cylinder... and bands... which further reduces the positive buoyancy.
I account 2lbs per al80 when adding weight to my sidemount. Half that for al40s.
To solve weighting, I get my students neutral with no cylinders at 3-6m. That ensures accurate weighting for exposure protection and other kit carried. In a 3mm full suit, it's 2-4lbs normally. Then we add 2lbs per AL80 and 1lb per AL40...depending on the dive we're doing.
None of that goes on a weight belt..
