Will 40 briquettes fit in one of those baskets? If not it won't get the PBC to the temp you want in my opinion. If it'll hold 40 ypu wont have issies with temperature. Also, even if it holds 40, you may wanna use both (they come in a set) especially if you are needing to cook for up to 2 hours......
Even still I'm not sure it'll work or not. The fire brick will radiate heat which allows for a more even temperature throughout the PBC just like if you used the whole basket. You'll notice a very minor difference from the coal side compared to the side without coals but it's minimal. I'm thinking the weber baskets will cause a greater temp different.
If you go to a brick yard, you can get the bricks Cheap. I got mine for $1.70 each....Lowe's and Home Depot are rip offs for fire brick.
Here's a couple pics.....It works well!