Of course it make sens since I don't think that a Maruzen type 96 clonde would pup out 540 fps out of the box.
But when I tried with my KJW M9 last year, with an high flow valve and stiffer srpings, I was exactly at the 350-370. I could pass through both sides of the can at gun point but not in the bottom central.
But maybe the thickness is never even from a can batch to an other another anyway