if the trunk is only 1 block wide at the bottom, it's very easy, make a new procedure, and make is something like: if block X Y-1 Z solid? with a return block, then go back to your tree structure, and in additional generation condition, you put your procedure, hope that helps!
if the trunk is only 1 block wide at the bottom, it's very easy, make a new procedure, and make is something like: if block X Y-1 Z solid? with a return block, then go back to your tree structure, and in additional generation condition, you put your procedure, hope that helps!
Thanks :D