A 26" would be a sweet mod, little extra room.
Incidentally, my love and admiration of this famous kettle rivals any of you. Knocking a door into the top of just any grill wouldn't work. When this thing is fired up the swirling flames and dynamics in there are pretty incredible. I think it's because of the symmetry, it's a blast furnace. I've been making this thing for years, I'm on my 4th version, each with slightly different shapes (shape of the opening) and variants (door closed/open, type of fuel, placement of stone/fuel, etc.). Friends donate them when they find one in the trash.
Here's a flatbread I made the other night,
http://instagram.com/p/kfnTJMsArZ/