My rig of softplate (OMS IQ Lite - $150) & wing (Aqualung Outlaw - $80) + 1 quick release tank strap ($25) weighs around 1.6kg/3.5lb (without the optional wing cover and no pocket) to 1.8kg/4lb (with the wing cover -$45 and 1 extra pocket for dsmb, torch, mirror, and whistle - I got this one for free). Everything is soft and can be easily packed flat or rolled up tightly, total $255-$300. I need 1-3kg of lead with this rig and a standard 11L alum tank, depending on wetsuit thickness (rash guard to 5mm semi-dry), so it's not super imperative to switch to a more negative rig.