You are right,
and I take everything into account in a racquet,
especially the swingweight which to me is the most important (it has to be at least 350 to really have a good feel of the racquet in swing)
I measured all my 4 racquets swingweight using TW method (done it with other racquets as well, in previous years, so I am pretty good at it)
the heavier ones are 350, 355
the light ones are 340 each.
I could feel this small difference before the measurements and I even estimated it quite right.
I dunno what to say about that 315 of one of yours but it just seams pretty impossible.