In my experience, the heat variance across a heatbed can be a bit of a nuisance with regard to achieving a suitable sticking temperature. However, usually you can get around it by bumping the temp a bit. What I've seen as a more common problem is height variation across a heatbed as it warms up. As commented, edges and corners are usually cooler, which means that those areas also expand less. This means you get greater expansion in the middle of the bed, and less at the edges, and in response, a bed will often dish a bit as temps increase.

When you do the larger prints, do you see any difference in "squish" in the filament as it is deposited on the bed?