I would look at Garnica Spanish company it weights 30 less than domestic poplar cores. Their poplar cores are plantation grown no dark mineral streak telegraphing thru veneers there is little to no voids and I find this plywood very stable and the thickness consistency is is about a B+ they only down side I found but over cam was screws stripping out easier so we drill 4mm holes for hardware screws problem solved.
I was a big Columbia product guy are years had all kinds of issues the new MPX cores to inconsistent is thickness for CNC. They finally have a seamless outer band of poplar before they fixed that I can't count how many ends I replaced I was using there Kcore calibration on that was about a B I had my fair share of delamination problems as well
I used States plywood for a short time there fir core doesn't work up here in New England but I have to say the calibration is a A+
In my area all the suppliers want to carry Garnica that says something about the product. I hope some day soon Columbia listens to all the cries for better cabiration and telegraphing problems I still like the company but losing faith that they will come up with something soon