Mudfire ][

It's bigger. 50% larger stomach, stupidly segmented into six separate chambers. As Donald Rumsfeld says, "One goes to war with the bricks one has."  It's flatter and wider at the bottom, and there are several such bottoms to consider.

Probably the first lesson involves the slump angle of wet mud: It's darn close to zero degrees.  As Mudfire II is going to be roughly (+pun) twice as tall, the willingness of mud to stick to brick is going to be a problem.