For this to work, you'd need to use render tiling, but this feature isn't implemented in TG2. Hopefully it will be in the future.
In the meantime, you can do crop renders, and then reassemble the pieces in a 2D app like photoshop. Just make sure GI is turned off, or it will add a slight haze effect to the edges of each rendered crop. I am hoping they fix this issue in future updates.
I wish they would do smaller incremental updates, rather than larger ones, so we'd slowly gain more features in TG2.