The diver must anticipate his inflation needs , part of good form which is the hallmark of the safe diver. Wings must not be too big or too small. A diver must start with a balanced rig which gives him every chance to deal with emergencies. In ocean or lake diving, steel tanks should never be used without a drysuit. Double wings are an invitation to a disaster - do not use them.
Elastic wings are a disaster waiting to happen.
They can not be operated safely by mouth, they lose their gas if ruptured, they can not be breathed like normal wings, and they cause more drag than normal wings. For ocean, aluminum 80's are the tank of choice. If more gas is needed, take an aluminum stage, but don't risk your life being over weighted at the beginning of the dive. The buoyancy characteristics of aluminum, especially when using helium , are such that a weight belt and or canister light will provide the necessary ballast which can be dropped in an emergency, making the rig only reasonably negative when full, neutral when empty, but swimable by dropping the weight. In cave, steel must be used with a drysuit and they must be negative enough to allow the diver to stay down in a low on gas emergency.