Thanks for the quick replies! Sorry this is late. I finally had a chance to test it again and everything seems close enough now. Just to clarify, I was seeing the sag at the middle of the bed (center along the y-axis). I could barely slide a sheet of paper between the nozzle and the left and right side of the bed, but could easily slide the sheet between the nozzle and the middle with room to spare. When printing in that middle area the filament wasn't sticking to the bed and was getting stuck to the nozzle and being dragged.

I was suspicious of the 10" bed maybe being too wide to only be supported at the corners. Doesn't sound like it's a concern though.

Thanks again,
Matt