Greg - nice work. It makes me regret not having CAD at home (and I'm not allowed to do this sort of playing around at work, sorry to say). I can do the work with pencil and paper, but frankly it will be more accurate to con, er, ask you to do it digitally. Would you be willing to re-do some of the work on the head-on view and calculating the tip clearance for each prop? Since the starboard engine is a bit closer to the camera than Amelia, and the port engine a bit futher away, their average should be exactly the same scale as Amelia.
Alternatively, but a bit more cumbersome, would be to relocate the line under her feet so that it is in the same vertical plane as the prop hubs and AE. You show the line under her feet as not quite parallel to a vertical plane passing through the prop hubs (note the apparent distance from each tire to the line that passes under her feet), which as you mentioned under-represents the dimension on the starboard side, and over-represents it on the port side. You also mentioned that moving the line toward the camera would increase the clearance number, but rotating the line about her feet, rather than simply moving it, would also correct the measurements on both sides and bring it into the same plane as AE and the other prop hub. Rotating the line will provide a more accurate vertical reference from each prop tip to ground. The vertical scale will be slightly different under each prop, but luckily the props themselves provide handy references.
LTM