DIFFERENT DIVES DIFFERENT TANKS ! I DIVE WITH AN AL 80 IN WARM/SHALLOW DIVES,,(80-100)-ANYTHING DEEPER, I USE TWIN 120CFT-(120-180)-ON MY OMS .. STEEL HAS WAY MORE ADVANTAGES OVER ALUMINUM, WEIGHT DISTRIBUTION IS ONE,TOTAL WEIGHT IS THE OTHER, -EXAMPLE, IF IM DIVING AT 120-180 ON A THREE MIL, I USE LESS WEIGHT (TOTAL)- IF IM DIVING AT 120-80- WITH A THREE MIL, THEN I USE A LITTLE MORE(4-6 LBS)WEIGHT - LESS COMPRESSION,,MORE BUOYANCY.