Hope I've got the right one
Simply cut down the inside (right side)of the first inner column (it's almost spot on 5inchs out from the right edge-see red line below) this will give you a neatish 5x5 building (i believe Denny has this in the instructions?):
or for a bit more work
Load the pdf into gimp at 300dpi
Delete from the left side upto the left side of that fist inner wall mark (that one we cut on right off above - just left of the red line above).
Scale the width only to 113% (should make it spot on 6 inchs with minimal distortion)
Print x 4 and assemble, trim top to fit
6x6 building:
Let me know if the above is way to confusing to follow and I'll clarify