Digital BW, The Print

I finally ran out of the stock of Kirkland glossy that I had bought
maybe 6 months ago, and picked up a couple of new boxes.  The
difference would seem to be trivial.  According to the boxes, the new
is 68 lb instead of 69, and 255 g/m2 instead of 260 g/m2.  But the new
stuff seems a lot more flexible, and a lot more prone to getting wavy
with even a moderate ink load - enough to make me glad I'm using 8-ply
mat.  Has anyone else out there noticed this? or maybe its just me
being a bit too picky?

Robert