 Tucking the cylinders under the arms reduces water resistance, potentially increasing kick efficiency.Sidemount divers using two cylinders will generally benefit from improved stability and balance due to the lowered center of gravity relative to backmount divers and improved trim due to the more adjustable designs of common sidemount harnesses.When using a single cylinder in sidemount some of that benefit is negated since balance is off, though with an aluminium cylinder and proper body tension single cylinder sidemount diving is easier and more comfortable than many divers expect.