That expansion rack would be great for low and slow cooks. But this might just get in the way for OP's need.
I would just pick up cheap used 18" and run them together. 26" has 508 sq.in. cooking surface. 22" has 363, and 18" has 240.
So, combined is 600sq.in which is more than 26". Fuel usage won't be much more either.
I would personally, go for cheap used 22", so I never run out of room.
My opinion only.