Mark, on the front, the guide will protude in fully pivoted position by app. 1mm (1/2" = 12,7mm), but this is measured from the plain of the middle of the front axle and your measurement with the 1/2" is starting from the guide stem middle.
what measurement did you guess from the middle of the front axle to the middle of the guide stem?
here are 2 pictures of the chassis right now, i think it should be possible to stay within your specs :)



the chassis are already on shapeways with your measurements.